Are Turbos Hard on Oil?

[OVERKILL]

Wife’s Nissan rogue turbo has a pre set maintenance minder to tick off at 10k… for oil changes. I use the adjustable one that’s configurable in either 250 or 500 mile increments I forget which but I just set that to 5k. I don’t need an algorithm to save me a few dollars on oil and a filter. Engines cost 1,000s

If it had a 10k mileage counter, it wasn't an iOLM.

The algorithm may not save you money, it may cost you more money, depending on the usage profile of the equipment. I don't think you understand the point I'm making here.

 

[97prizm]

Seems like a silly question, but I figured I'd ask anyways. We just picked up a used 2018 Chevrolet Equinox with 91k miles from a dealer. 1.5l Turbo LYX. Oil was freshly changed when we bought it....no signs of sludge from what I could see through the oil filler. Runs great. No complaints.

I just did the 1st oil change this past weekend at 1k miles to get the unknown dealer commodity stuff out of there and put in some Valvoline Restore and Protect to clean up any deposits. Unknown maintenance but I figured a few OCI's of Valvoline Restore and Protect wouldn't hurt.

When we bought it the oil was brand new looking. After 1k miles it had darkened significantly on the dip stick and when i drained it it looked very dark, like it was due for an oil change. The other thing I was surprised at was how HOT the oil was!!! I normally take my vehicles for a short drive to get the oil good and warm/hot before changing.

This oil was super hot! I could barely turn the drain bolt by hand it was that hot. Surprised me a bit actually.

So that brings me to my question. Are turbo engines harder on oil than non-turbo engines? If so, what in the oil tends to wear down fastest? Does it shear faster than non-turbo'd engines? Does the oil oxidize faster? Anything else I'm not aware of? Just looking for some education. Thanks!

**EDIT** I should mention we don't drive the car aggressively but my wife does A LOT of short trips and idling. So for that, we fall in the severe maintenance category. I drive it to work once per week on the highway (45 miles each way) for the fun of it.

If they're water cooled and current then modern turbos are less hard on the oil then the old school oil cooled turbos of the past. Yes they can get really hot. A good synthetic is a must.

 

[Wireman1987]

If it had a 10k mileage counter, it wasn't an iOLM.

The algorithm may not save you money, it may cost you more money, depending on the usage profile of the equipment. I don't think you understand the point I'm making here.

What you’re saying is the OLM may suggest changing oil too soon? Not my vehicle so I’m not going to sweat it too bad… I just recently had my work van serviced at fleet was 3500 miles over based on our fleets service tracker. What happened is I took the van over from a co-worker who was out on a medical and being the vehicle sat the OLM figured the oil to be fine. We’re told to follow OLM’s guess the company feels they’re saving coin. Now I hear we’re going back to 5,000 mile services with emails sent to our work email for a reminder.

 

[OVERKILL]

What you’re saying is the OLM may suggest changing oil too soon? Not my vehicle so I’m not going to sweat it too bad… I just recently had my work van serviced at fleet was 3500 miles over based on our fleets service tracker. What happened is I took the van over from a co-worker who was out on a medical and being the vehicle sat the OLM figured the oil to be fine. We’re told to follow OLM’s guess the company feels they’re saving coin. Now I hear we’re going back to 5,000 mile services with emails sent to our work email for a reminder.

There are two types of OLM's:

1. Mileage counters (the type you described). These work of a fixed mileage interval and are just fancy versions of a window oil change reminder sticker.

2. iOLM's (intelligent Oil Life Monitors). These calculate the oil life left based on a number of parameters, which vary by OEM, including, in some instances, contamination with an "eye" in the oil (BMW), but typically use time at temperature, # of cold starts, oil temperature, engine hours, driving style...etc.

Oils don't degrade in miles. An engine doesn't wear in miles. A vehicle running but not moving is adding no "miles" to the interval, but is accruing hours on the fluid, adding contaminants via blowby, shearing VII polymers, subjecting the lubricant to conditions that produce coke, varnish and lacquer in the ring lands. But this isn't factored into the interval.

This is why large industrial machines use engine hours instead (or in some instances, litres or gallons of fuel burned), as it's a considerably better proxy for wear than "miles". We only use miles because it's convenient and ingrained into people's minds, and this in turn is because, in probably the vast majority of cases, it gets your car into the garage where they can ding you for other maintenance items you may or may not need, which may or may not be a good thing depending on the honesty of the shop and how well you maintain your vehicle.

So, an iOLM could have you changing the oil sooner, or later, than a mileage based counter, because it's going by the conditions of use, not the number of rotations the tires have made.

Example from my wife's truck:
Longest iOLM interval: 14,031km (8,718 miles) - This was over the course of 5 months (March through August). Tons of highway driving including 2x 15hr drives, one to the east coast, one back. Many trips to the cottage.

Shortest iOLM interval: 9,974km (6,198 miles) - This was over the course of 8 months (November through July). More short tripping, winter driving conditions, so lots of remote start use.

So, that's a difference of >2,500 miles in OCI length due to operating conditions.


This brings me back to my original question to you: Would you not differentiate between the two operating profiles I cited? Because an iOLM would.

If we look at this in engine hours, we'll take my wife's last interval:
June 2024 to May 2025. 19,733km (12,262 miles)
Hours: 719

So, that's an average speed of 17mph.

So let's use an hours-based approach here to examine my previous query: Our condemnation limit is going to be 500hrs.

1. In-town driving, average speed of 8mph. 500 hours gets us to 4,000 miles.
2. All-highway driving, average speed of 50mph. 500 hours gets us to 25,000 miles (hello AMSOIL and M1 EP!)

In both instances, the engine, and its lubricant, is seeing the same number of hours. #1 would be burning more fuel, have way more warm-up cycles (start/stop), and generally poorer conditions for the oil. #2 is basically the "ideal" operating profile.

So, changing oil #1 at 5,000 miles is changing it LATE, while changing oil #2 at 5,000 miles is changing it EARLY. If we go by engine hours.

This is the sort of thing that iOLM's were developed to address.

 

[Patman]

5k-6 month is a good window

A turbo car that’s driven mostly on the highway is really not going to beat up the oil too badly. That turbo won’t be getting into the boost very often. So you could go longer than 5k quite safely with a good oil.

 

[Wireman1987]

It’s something I never put too much thought into. I was always a 2x year or 5k mile oci guy. Works out to 2 oil changes per year

 

[Patman]

It’s something I never put too much thought into. I was always a 2x year or 5k mile oci guy. Works out to 2 oil changes per year

I put 25k on my Civic per year and about 8k on my Corvette. And I drive mostly highway. So a 5k interval in both cars would be too much (especially since I can’t change my oil at my condo so I have to drive to my dads house to do oil changes)

So I follow the OLM in both and that typically means 9-10k in the Civic and 7k in the Vette.

 

[OVERKILL]

It’s something I never put too much thought into. I was always a 2x year or 5k mile oci guy. Works out to 2 oil changes per year

Most people don't, that's why they haven't considered why changing by mileage might not be the best idea.

 

[GR_CoB]

So that brings me to my question. Are turbo engines harder on oil than non-turbo engines? If so, what in the oil tends to wear down fastest? Does it shear faster than non-turbo'd engines? Does the oil oxidize faster? Anything else I'm not aware of? Just looking for some education. Thanks!

Generally oils do shear faster in turbo engines. But then it does also matter who made the turbo. Case on point: one of my coworkers had two turbo vehicles, a Honda CRV 1.5L and a foxbody Mustang SVO 2.3L. Both get driven hard, CRV gets more mileage as it's a daily driver. CRV just had the turbo replaced under warranty, while the original turbo in Mustang from 1985 still marches on. Similar mileage on both currently, just the age and technology gap.

 

[Blagoje]

So you wouldn't differentiate between a turbo vehicle driven 100% highway vs one driven 100% in town? Because the number of engine hours accrued to get you to 5,000 miles would be markedly different here.

How am I supposta get my money out of my 5 quart jug of oil that I paid $15 for after a $10 rebate if I don't go 6,000 miles instead of 5,000 miles?

Instead of thick versus thin discussions we need to have heated debates between short OCI trippers and extended OCI heroes!

BITOGERs are starting to slack

 

[burbguy82]

Actually - I think they are running much cooler. The oil is being cooled in modern engines and the turbo bearing housings are being cooled. It’s still very hot in there, but not as hot as it was in the days of turbos being cooled only by the oil.

This is where I agree with your past statements about cooling being a large part of system durability......a high output per liter, say 100 hp per liter of displacement, will require more cooling capacity than an engine that is at 35 hp per liter......to maintain the same level of durability.

Big rigs are huge displacement turbo diesels, that commonly last millions of miles, on dino 15w40 oil

 

[Hohn]

Many engines have an auxiliary electric water pump that keeps circulating after the car is turned off.
API got better, but in turbo engines, I would run only Euro oils.

There are also some clever schemes that use thermal siphoning to circulate coolant and/or oil at shutdown.


To the OP—

There was once I time, long before water-cooled turbos that turbos would put a lot of heat into the oil because the turbos were both oil lubed as well as oil-cooled. This is the bad old days of turbo timers and such.

These days almost every OEM turbo is water-cooled, and the oil flow rate through the bearing housing is a tiny fraction of what it once was with oil cooled turbos. It just doesn’t take that much oil to lube the turbo, as most of the oil flow was there to cool it, not lube it. And if the turbo should happen to be a ball bearing unit instead of journal bearing, the oil flow is a tiny, tiny trickle (hence the restriction orifices in most BB turbo kits). The lack of viscous drag is the primary reason BB turbos have such quick response.

Because the majority of the turbo’s heat is sunk to the cooling system and the oil flow is relatively modest, the actual temperature rise of the oil through the turbo is pretty modest. If I recall correctly from my turbo temp mapping test back in the early 2010s, the temperature rise is only about 40F-50F comparing oil temp in vs out.

So if you measured OEM turbo oil temps, I’d be shocked if you saw anyhing 150C or higher on the drain side on any street-bound normal daily driver.

On a track car, it’s different— you might see 150C in the pan and 170C coming out of the turbo drain. That’s pretty dang hot. But a good oil like HPL can handle it.

 

[Hohn]

This is where I agree with your past statements about cooling being a large part of system durability......a high output per liter, say 100 hp per liter of displacement, will require more cooling capacity than an engine that is at 35 hp per liter......to maintain the same level of durability.

Big rigs are huge displacement turbo diesels, that commonly last millions of miles, on dino 15w40 oil

15L and typically top out at 600hp. So roughly 40hp/L. Plus, being diesel, they have a high expansion ratio and the EGTs are quite a bit lower than a gasoline equivalent. At full tilt WOT, most modern diesels will top out EGT at 750C or less. And then at normal part load steady highway, they’ll be back to 400C or so (hotter now with catalysts and such needing the hotter temps, used to be more like 300C or less at light load cruise).

Gasoline engines are going to sustain 600C plus in most cases, and generally have higher average exhaust temps in street-based vehicles. Plus much higher power density.

 

[burbguy82]

15L and typically top out at 600hp. So roughly 40hp/L. Plus, being diesel, they have a high expansion ratio and the EGTs are quite a bit lower than a gasoline equivalent. At full tilt WOT, most modern diesels will top out EGT at 750C or less. And then at normal part load steady highway, they’ll be back to 400C or so (hotter now with catalysts and such needing the hotter temps, used to be more like 300C or less at light load cruise).

Gasoline engines are going to sustain 600C plus in most cases, and generally have higher average exhaust temps in street-based vehicles. Plus much higher power density.

The Cummins site is where I was getting my info, to my 35 hp per liter is accurate as a low to mid average, still way less than 100hp per liter, which was my point. Most trucks however are in the 200-300 hp range, talking medium duty trucks, much less yet still.

Heat is the killer

Your argument is more based on the system that generates the heat and thereby the efficiency loss, I am talking about the cooling system.

 

[Hohn]

The Cummins site is where I was getting my info, to my 35 hp per liter is accurate as a low to mid average, still way less than 100hp per liter, which was my point. Most trucks however are in the 200-300 hp range, talking medium duty trucks, much less yet still.

Heat is the killer

Your argument is more based on the system that generates the heat and thereby the efficiency loss, I am talking about the cooling system.

Sorry I misunderstood you. Higher power density does indeed put a bit more load on the cooling system.

I have a soft spot for the X15 as the fuel system development of the 2010 model year was my first job at Cummins. While we had a talented team of people doing the entire fuel system, I was the primary person responsible for the HP fuel system plumbing-- the HP lines, the HPC crossovers through the cylinder head, feeding the injectors, the rail and rail mounting, etc. I ended up having some responsibility for the HP fuel pump bracketry and such before it went to production.

The smell of fuel must have stuck, as my entire career since then (with the exception of a 3 year period) has involved fuel system engineering and development.

 

[OZHSV]

My Tiguan is my first and curiously it is the default display on the screen.

My ‘23 Audi A4 45TFSI has this as well.

Strangely however, it consistently reads 15-20° Celsius less than what the OBD11 reports when probing engine live data.

I suspect this (the dash gauge reading lower) is deliberate to (attempt to) discourage hard driving prior to the oil being given the full opportunity to reach the optimal temperature

 

[gunnellett]

A turbo car that’s driven mostly on the highway is really not going to beat up the oil too badly. That turbo won’t be getting into the boost very often. So you could go longer than 5k quite safely with a good oil.

What's interesting is I get very little to no boost with my truck unless I am towing or up to highway speeds.

It's also the only time my oil temp gets over 200F and it takes a while to get it there.

96 F350 Powerstoke.

 

[gunnellett]

15L and typically top out at 600hp. So roughly 40hp/L. Plus, being diesel, they have a high expansion ratio and the EGTs are quite a bit lower than a gasoline equivalent. At full tilt WOT, most modern diesels will top out EGT at 750C or less. And then at normal part load steady highway, they’ll be back to 400C or so (hotter now with catalysts and such needing the hotter temps, used to be more like 300C or less at light load cruise).

Gasoline engines are going to sustain 600C plus in most cases, and generally have higher average exhaust temps in street-based vehicles. Plus much higher power density.

With my 7.3 Powerstoke diesel, I've read time and time again to keep EGT below 675C (1250F) unless it is for a very short period of time to get over a mountain pass when towing or a similar scenario.

In general, what would be different between a diesel and a gas engine allowing a gas engine to run a higher EGT with less concern? I was under the impression the high EGT concerns for diesels has to do with the limits of the metal (I've read the scary word "melting") but I would have thought this would be similar with gas engines at similar temps.

 

[Hohn]

With my 7.3 Powerstoke diesel, I've read time and time again to keep EGT below 675C (1250F) unless it is for a very short period of time to get over a mountain pass when towing or a similar scenario.

In general, what would be different between a diesel and a gas engine allowing a gas engine to run a higher EGT with less concern? I was under the impression the high EGT concerns for diesels has to do with the limits of the metal (I've read the scary word "melting") but I would have thought this would be similar with gas engines at similar temps.

That's pretty conservative. In most diesels of that vintage, 1250F can be handled all the time, day in, day out. You really won't see any trouble until 1400+ and only if sustained for at least a minute or more. Lots of us back in the day regularly had short excursions to 1600F + without any issues at all, because EGT per se isn't the issue, it's piston temp. (and on B series Cummins, exhaust valve temps)


What's different about diesels is the nature of combustion. Diesels have a diffusion flame combustion-- the fuel has to mix *as* it burns. Indeed, it has to mix to burn, otherwise it just turns to smoke (liquid charcoal vapor-- it's fuel that got hot enough to burn, but didn't have oxygen at the time). This means some fuel has to hang out and wait for some oxygen to come along to support burning. This is a major reason for the lean air fuel ratios of diesel combustion are used-- this makes it easier for a given amount of fuel to find the oxygen needed to burn. That makes for a faster burn rate and more efficient combustion. Unfortunately, this also tends to cause NOx from high amounts of excess o2 available to combine with N2 to form NO2 or NO3. This happens above about 1700K flame temp.

This is different from premixed combustion like gasoline, which has a flame front that propagates from a single initiation source (spark plug).


For a given EGT, then, diesels tend to have higher piston temperatures because the combustion event is longer and higher pressure average pressure and can drive more heat into the pistons.

Diesels are "high torque" because of this elevated average pressure (BMEP) relative to the peak pressure.

And the elevated piston heat is why most industrial diesels are now monotherm steel piston designs, with aluminum pistons reserved for relatively light duty engines (aluminum has poor fatigue life when hot).

 

[gunnellett]

That's pretty conservative. In most diesels of that vintage, 1250F can be handled all the time, day in, day out. You really won't see any trouble until 1400+ and only if sustained for at least a minute or more. Lots of us back in the day regularly had short excursions to 1600F + without any issues at all, because EGT per se isn't the issue, it's piston temp. (and on B series Cummins, exhaust valve temps)


What's different about diesels is the nature of combustion. Diesels have a diffusion flame combustion-- the fuel has to mix *as* it burns. Indeed, it has to mix to burn, otherwise it just turns to smoke (liquid charcoal vapor-- it's fuel that got hot enough to burn, but didn't have oxygen at the time). This means some fuel has to hang out and wait for some oxygen to come along to support burning. This is a major reason for the lean air fuel ratios of diesel combustion are used-- this makes it easier for a given amount of fuel to find the oxygen needed to burn. That makes for a faster burn rate and more efficient combustion. Unfortunately, this also tends to cause NOx from high amounts of excess o2 available to combine with N2 to form NO2 or NO3. This happens above about 1700K flame temp.

This is different from premixed combustion like gasoline, which has a flame front that propagates from a single initiation source (spark plug).


For a given EGT, then, diesels tend to have higher piston temperatures because the combustion event is longer and higher pressure average pressure and can drive more heat into the pistons.

Diesels are "high torque" because of this elevated average pressure (BMEP) relative to the peak pressure.

And the elevated piston heat is why most industrial diesels are now monotherm steel piston designs, with aluminum pistons reserved for relatively light duty engines (aluminum has poor fatigue life when hot).

That is an awesome detailed explanation that made complete sense. Thank you!