OCI: Engine Hours vs. Mileage

[The Critic]

For those of us with engine hour meters on our vehicles, should you use engine hours instead of mileage for determining OCI's?

For instance, it has been 2,067 miles since my last oil change. According to my cluster, it has been 82 engine hours. If I proceed with my usual 5K OCI, it will be about 200 engine hours.

 

[H. Swanson]

I have the same question actually. I have a Hyundai Santa Fe TGDI 2.0 with the dreaded Theta II engine. I put maybe 500 miles on it per month, mostly short trips. If I go with the Severe recommendation, it's 3 months or 3k miles. If I go by mileage, that's 6 months. Do I still go by 3 months with only 1,500 miles on it? Not sure what the best path is.

 

[The Critic]

I have the same question actually.

Do you have an engine hour meter?

 

[Rand]

I have the same question actually. I have a Hyundai Santa Fe TGDI 2.0 with the dreaded Theta II engine. I put maybe 500 miles on it per month, mostly short trips. If I go with the Severe recommendation, it's 3 months or 3k miles. If I go by mileage, that's 6 months. Do I still go by 3 months with only 1,500 miles on it? Not sure what the best path is.

That isnt the same question and depends on how you drive the 1500 miles.
Theoretically you could do an oil change at 500 miles if you idled for 300 hours (hour meter part of OP's post)

Back on topic:
For most it doesnt matter
I would use miles unless its idled extensively(80+ hours) in which case I would convert at ~25miles/hour of idling and add that to the miles.

 

[H. Swanson]

Do you have an engine hour meter?

I don't think I do.

 

[atikovi]

Seeing that few cars have hour meters, I don't know any manufacturer that specifies oil changes by that interval. If it sees lots of idling like a police car, it's usually 3,000 mile ocis.

 

[doitmyself]

Does this concur with your owner's manual? It is a starting point.

1500 Models Only NOTE: Under no circumstances should oil change intervals exceed 10,000 miles (16,000 km), twelve months or 350 hours of engine run time, whichever comes first. The 350 hours of engine run or idle time is generally only a concern for fleet customers.
2500 - 3500 Models Only NOTE: Under no circumstances should oil change intervals exceed 8,000 miles (13,000 km), twelve months or 350 hours of engine run time, whichever comes first. The 350 hours of engine run or idle time is generally only a concern for fleet customers.
Severe Duty All Models NOTE: Change Engine Oil at 4,000 miles (6,500 km) if the vehicle is operated in a dusty and off road environment or is operated predominantly at idle or only very low engine RPM's. This type of vehicle use is considered Severe Duty.

I agree with Rand. Consider the hour meter if your vehicle sits idling a lot, like a police or taxi vehicle. Otherwise, I start with my owner's manual recommendation and adjust my OCI based on all the factors we share and learn about here. I.E., I'm personally not comfortable going over one year in my climate (hot/cold) and driving parameters (low annual miles, mixed urban/highway miles). I don't follow my oil change minder either since I am not confident about its algorithms. It's a personal decision and not something you can quantify 100% IMO.

Your data indicates you don't do lots of highway miles and your 5K OCI maybe is indicative of that. IF these miles were hauling severe, heavy loads, you would probably consider even a shorter OCI. You probably could go a bit longer, depending on oil choice.

 

[fsdork]

This is from the manual for a 2011 Ford Crown Victoria:

"For every hour that the vehicle idles, it has accumulated the equivalent of approximately 33 miles (53 km) of driving.

Example: When the odometer has accumulated 3,000 miles (4,800 km) and the idle meter shows 61 hours, a 5,000 mile (8,000 km) oil change interval will have been reached: 3,000 road miles (4,800 road km) + (61 idle hours x 33 miles [53 km]/idle hour) = 5,013 miles (8,067 km)."

Applying this to a vehicle with a different recommended OCI (distance) would of course require some adjustments to the numbers. Also, it would be important to determine if your vehicle's hour meter only counts idle time, or total run time. In the case of the Crown Vic, the manual refers to it as an "Engine Idle Hour Meter".

 

[The Critic]

Does this concur with your owner's manual? It is a starting point.

I agree with Rand. Consider the hour meter if your vehicle sits idling a lot, like a police or taxi vehicle. Otherwise, I start with my owner's manual recommendation and adjust my OCI based on all the factors we share and learn about here. I.E., I'm personally not comfortable going over one year in my climate (hot/cold) and driving parameters (low annual miles, mixed urban/highway miles). I don't follow my oil change minder either since I am not confident about its algorithms. It's a personal decision and not something you can quantify 100% IMO.

Yes.

For reference, my OLM currently shows 79% remaining.

 

[dubber09]

I personally do oil changes at 150 engine hours or 4K miles, whichever comes first. In my case it's very close but miles come first.

 

[paulo57509]

I have seen maintenance schedules written in terms of both miles and or time.

4 months = ~3000 hours. The only time I have ever followed an elapsed time OCI is with construction, garden equipment, watercraft, etc.

 

[Hohn]

For those of us with engine hour meters on our vehicles, should you use engine hours instead of mileage for determining OCI's?

For instance, it has been 2,067 miles since my last oil change. According to my cluster, it has been 82 engine hours. If I proceed with my usual 5K OCI, it will be about 200 engine hours.

Neither. Fuel burn is more accurate than either hours or miles, IMO.
Burning fuel is the source of all contaminants in the oil, right?

It seems to me then that normalizing OCI by fuel burn per unit crankcase capacity makes a lot of sense. One RoT proposed by an engineer I respect was 50 gallons of fuel per quart of capacity.

Kind of makes sense. Five qt capacity at 30mpg means (5*50*30=) 7500 OCI. But at 20mpg it would only net you 5k OCI.

 

[The Critic]

Neither. Fuel burn is more accurate than either hours or miles, IMO.
Burning fuel is the source of all contaminants in the oil, right?

It seems to me then that normalizing OCI by fuel burn per unit crankcase capacity makes a lot of sense. One RoT proposed by an engineer I respect was 50 gallons of fuel per quart of capacity.

Kind of makes sense. Five qt capacity at 30mpg means (5*50*30=) 7500 OCI. But at 20mpg it would only net you 5k OCI.

I don't disagree. I believe @High Performance Lubricants made a similar statement a while ago. However, what should we use as a baseline?

With a recent change in usage patterns, I have been averaging about 14 mpg. This would put fuel burn at around 350 gallons for a 5K interval.

4 months = ~3000 hours. The only time I have ever followed an elapsed time OCI is with construction, garden equipment, watercraft, etc.

Actual time and engine run time are two entirely different things.

 

[tnt_motorsports]

I subscribe to the KISS method here. I change my oil when the EVIC says so on my Ram and the T&C and every 5K on the ole Jeeper.

Just my $0.02

 

[b_b]

ive looked into those emperical formulas for oil change interval before. they generally coincide with what my oil life monitor tells me on my f150.

 

[Quattro Pete]

I don't disagree. I believe @High Performance Lubricants made a similar statement a while ago. However, what should we use as a baseline?

It's been a while, but remember TooSlick's OCI formula? We built a calculator that incorporated it a while back.

It takes MPG (effectively representing amount of fuel burned) into account, among other things like engine displacement, oil sump capacity, etc.

Calculator

 

[StarCaller]

Toyota Prius, Castrol Edge 0w-40
Good to know that I could go easily 10.000 miles, but I'll be rather safe than sorry & stay with a 5.000 miles (every 10 month) interval /

 

[H. Swanson]

That isnt the same question and depends on how you drive the 1500 miles.
Theoretically you could do an oil change at 500 miles if you idled for 300 hours (hour meter part of OP's post)

Back on topic:
For most it doesnt matter
I would use miles unless its idled extensively(80+ hours) in which case I would convert at ~25miles/hour of idling and add that to the miles.

I have no abnormal amount of idling. It's just short trips to and from school by my kids, the gym, etc. Usually under 5 miles.

 

[The Critic]

It's been a while, but remember TooSlick's OCI formula? We built a calculator that incorporated it a while back.

It takes MPG (effectively representing amount of fuel burned) into account, among other things like engine displacement, oil sump capacity, etc.

Calculator

Interesting. Based on a "typical SP synthetic oil" with a TBN of 6.0:

 

[dumkid]

How do these calculations compare to the manufacturer OCI recommendations?