Is 5w30 "better" than it used to be compared to 10w30?

[railfan844]

On many vehicles specifying an SAE 30 multigrade, 5w30 (as opposed to 10w30) used to not be recommended for anything except very cold places. Has this changed with the advent of modern synthetics?

I own three 1988-89 Toyotas (7MGE, 22RE) and a 1997 Subaru Legacy with a rebuilt N/A EJ22.

All of the manuals for these vehicles specify 10w30 or 10w40 for ambient temperatures from around 0*F to around 100*F.

They specify 5w30 for under 0*F but not for over around 60*F. Additionally, my Subaru's manual says 5w30 is "not recommended for high speed driving". High speed driving is not defined in any way. This is apparently a semi-common point of discussion among Subaru boards and owners of this gen model. Again this manual was written in '97.

I am in Western Washington and (possibly due to climate change) the winters have been getting colder (0-15*F highs, lower with wind chill) and the summers have been simultaneously getting hotter (over 100*F, especially in traffic).

Here is my question:

Can I trust a modern, full synthetic 5w30 year round in these vehicles, should I follow the manual and stick with a 10w30 in the summer or possibly all year, ...or should I look into something different still like a 5w40 or 0w40? How could I tell?

My guess as to why the 10w oils are recommended by the manuals (written in 1988, '89, '97, etc) is because the older 5w30 oils used to shear down more than the 10w's. According to my best research, the modern synthetic 5w30 oils we have simply don't have this problem anymore and are miles ahead of what they had when they wrote those manuals.

10w30 is harder to find, and I already have a large stock of M1 EP and EP HM 5w30. I'm also concerned about cold starts. This last winter was extremely cold (for where I live), but I felt very safe with the 5w in all my sumps. On the other hand I'm also concerned about my M1 5w30 not being adequate to protect in 104*F stopped traffic this summer.

I have already been running 5w30 year round in all three vehicles for several years with no issues (yet) but have not done any UOAs.

I also have a new 7MGE that just got built and I am very unsure of what oil to use in it after the break in. It is brand new. Builder recommended 10w30, but said 5w30 will "work". I believe the builder was simply following what the manual said and did not have any further reason for the 10w30 recommendation.

I don't race or drive my vehicles hard outside of a street setting, but I do drive them relatively hard on the street.

I am extremely on top of changing oil ahead of schedule based on mileage, engine hours, and trip length. I always stay on the low side of OCIs.

Has anyone else been in my situation? What viscosity should I choose? Keep the 5w30 and make it simple, or suck it up and start buying 10w30 or even something else in the interest of better engine protection? What could I do to better learn how to choose for myself? I'm completely lost on what I should decide on. I have also seen many conflicting opinions on this matter for each individual engine that I have in question.

Thanks.

 

[FowVay]

Vehicle manufacturers are required to meet specific fuel economy and emissions mandates for everything they sell. Oil viscosity grade plays a big part in this compliance. Modern vehicles specify lower and lower viscosity grades in an effort to meet the standards set forth by the government.

This is no more evident than in the diesel market where the gold standard was formerly a 15W-40 grade oil and now is a 5W-40 and trending toward 10W-30 and 5W-30.

Gasoline vehicles have gone from the 10W-40's of the 1980's down to 0W-20 and even 0W-16 in the 21st century. These changes didn't come about because the former viscosity grade was inadequate. These changes are done for fuel economy and emissions compliance.

In your situation, you can use any viscosity grade you choose provided the choice is within reason. A well designed 5W-30 would be perfect for you. In warmer months the 10W-30 would also be perfectly fine. Most of the modern specifications only apply to viscosity grades of 5W-30 and lower because that is what the manufacturers specify. For this reason you'll not find GM Dexos-1, Honda HTO-06, or any other specification that mandates a fuel economy improvement, on a 10W-xx grade oil. It doesn't mean they're not excellent oils, they're simply not specified by an OEM because they don't provide the fuel economy improvement or emissions levels caused by increased fuel burn that the government mandates.

You're lucky that you don't have to worry about low speed pre-ignition or filthy intake runners caused by the implementation of direct injection. You can choose a full-SAPS oil with a nice, robust additive package in practically any viscosity grade listed in the owner's manual. If you're not racing down the autobahn at V-max or cutting the stop lights with cat-quick reaction times then choose a low viscosity grade such as a 5W-30. If you're feeling adventurous then buy something with the most manufacturer approvals and sleep well knowing you have a well lubricated and efficient running vehicle.

 

[ChrisD46]

Besides CAFE requirements for vehicle manufacturers to meet , I wonder if better engine machining with closer metal clearances as well as tolerances held , along with possible smaller oil galleys being designed has much to do with thinner oils being recommended ? Conversely , we also see forum members leaving from American / Asian made vehicles owner's manual recommendations for the even "thicker" Euro 0W40 , 5W40 oils being used without any apparent engine damage - so the "Goldilocks" search for just the right amount of oil film strength by choosing what users think is the correct oil weight and oil brand for their driving conditions continues ... Short Answer ? I'd try Mobil 1 0W40 FS , a popular oil here that many equate to a higher end 30 weight oil behavior (or a thinner 40 weight) .

 

[Jetronic]

It's a HTHS thing.

SAE 30 and the 5W-40 have a HTHS around 3.5 cP or higher. Your typical off the shelf 5W-30 doesn't. However, if you can find an ACEA A3/B4 or C3 5W-30 it'll have a minimum of 3.5 cP aswell. Apparently this matters to Subaru.

10W-30 is or was likely to have a higher HTHS aswell, but maybe not quite above 3.5 cP.

 

[Jetronic]

Vehicle manufacturers are required to meet specific fuel economy and emissions mandates for everything they sell. Oil viscosity grade plays a big part in this compliance. Modern vehicles specify lower and lower viscosity grades in an effort to meet the standards set forth by the government.

This is no more evident than in the diesel market where the gold standard was formerly a 15W-40 grade oil and now is a 5W-40 and trending toward 10W-30 and 5W-30.

Gasoline vehicles have gone from the 10W-40's of the 1980's down to 0W-20 and even 0W-16 in the 21st century. These changes didn't come about because the former viscosity grade was inadequate. These changes are done for fuel economy and emissions compliance.

In your situation, you can use any viscosity grade you choose provided the choice is within reason. A well designed 5W-30 would be perfect for you. In warmer months the 10W-30 would also be perfectly fine. Most of the modern specifications only apply to viscosity grades of 5W-30 and lower because that is what the manufacturers specify. For this reason you'll not find GM Dexos-1, Honda HTO-06, or any other specification that mandates a fuel economy improvement, on a 10W-xx grade oil. It doesn't mean they're not excellent oils, they're simply not specified by an OEM because they don't provide the fuel economy improvement or emissions levels caused by increased fuel burn that the government mandates.

You're lucky that you don't have to worry about low speed pre-ignition or filthy intake runners caused by the implementation of direct injection. You can choose a full-SAPS oil with a nice, robust additive package in practically any viscosity grade listed in the owner's manual. If you're not racing down the autobahn at V-max or cutting the stop lights with cat-quick reaction times then choose a low viscosity grade such as a 5W-30. If you're feeling adventurous then buy something with the most manufacturer approvals and sleep well knowing you have a well lubricated and efficient running vehicle.

Subaru engines are notorious for failing, I wouldn't go down to a lower viscosity as it won't help any in avoiding failures. I would not consider mainstream 5W-30 adequate for these engines

 

[aquariuscsm]

I remember way back when Nissan "back specd" (if I'm using that term correctly) all their cars to 5W30, the TSB said something like "All Nissan vehicles are recommended 5W30 except 300ZX". They kept the 10W30 spec for that car.

 

[rumcapital23]

maybe a 504/507 spec'd 5W-30?

 

[PimTac]

Both 5W-30 and 10W-30 are 30 grade oils. The first number is the Winter rating. You should have no problems running a 5W-30.

The temperatures are going through normal variations here. I’ve seen close to zero many years ago. It also depends on where you live as Western Washington has a lot of microclimates.

Choice of oil should also take in to account where you might be. If you live in Seattle but frequently travel to the east side of the state or spend time in the mountains then the cold temperatures you experience will be even colder.

 

[kschachn]

Another thick vs. thin thread with a dose of winter rating on the side.

 

[dnewton3]

You cannot fairly and accurately compare/contrast lube reccomendations from 35 years ago, relative to today's, without acknowledging that so many things have also changed.
- chemistry advancements in the lubricant additives
- agency requirements in regard to emmissions
- agency requirements in regard to fuel economy
- processing improvements in the lubricant industry
- design improvements in the ICE industry
- process improvements in the manufacturing industry; both lubes and engines
Essentially, all these things combine to make a disconnected conversation between 1988 and 2023.

All that said, if those cars could run well on the lessor quality 10w-30 lubes of yesteryear, they'll do fine with today's 5w-30.
You're splittin' hairs where it's both unnecessary and illogical.

 

[InspectoRob]

Go to the BITOG homepage and under 'Articles' pull up Motor Oil University.
Remember, the first number is the cold visc. and that is only relevant for a short time from startup to warm. Cold weather you 5 or even 0 visc. so it circulates quickly. At running temp. you want 30 as specified by manufacturer. So simple - use 0w30 or 5w30 winter and 5w30 or 10w30 summer. I have had subarus for a long time (had 1988 GL, then 1995 legacy 2.2, then 2004 impreza ST wagon, now 16 WRX) and I used M1 5w30 and past 10 years M1 0w30. The 0w30 is great for reducing the subaru ticking, sewing machine sound, valves at startup - especially when cold. Your older subarus may benefit too. Be brave and try 0w30 Mobil 1 AFE (walmart $26 for 5qt jug)!

 

[JGmazda]

My 2001 Buick LeSabre uses 10w-30 year round out here in AZ. Like the OP, I often wonder if there's any advantage (Or disadvantage) to using a 5w-30 oil.

More importantly, oil formulations have changed a great deal over the last twenty years. I'm wondering not so much about viscosity, but of decreased (less wear protection) additives that "may" be beneficial for older vehicles. Perhaps today's modern 5w-30 oils are geared to DI engines and emissions vs. other factors.??

Obviously, my 3800 series engine isn't a highly stressed turbocharged engine, and with proper OCI's will last a long time...

 

[camrydriver111]

I would run 5W30 without worrying.

Especially if you are doing short OCIs, you will not run into the shearing issues.

 

[railfan844]

I'd try Mobil 1 0W40 FS , a popular oil here that many equate to a higher end 30 weight oil behavior (or a thinner 40 weight) .

I am very curious about the 0w40, however some of my engines use a little oil which according to my research makes the 0w40 unsuitable for them because of the SAPS content. I'm still not quite educated on this, so I need to do more research. It is on my list of things I want to try out for sure, especially if I plan on doing any harder driving.

You're lucky that you don't have to worry about low speed pre-ignition or filthy intake runners caused by the implementation of direct injection. You can choose a full-SAPS oil with a nice, robust additive package in practically any viscosity grade listed in the owner's manual. If you're not racing down the autobahn at V-max or cutting the stop lights with cat-quick reaction times then choose a low viscosity grade such as a 5W-30. If you're feeling adventurous then buy something with the most manufacturer approvals and sleep well knowing you have a well lubricated and efficient running vehicle.

I agree with this. I'm very happy with my non-GDI, non-California emissions compliant vehicles. My 22RE will run all day on just about any oil I give it. I just like 5w30 for the climate here, peace of mind with how cold it's getting.

Subaru engines are notorious for failing, I wouldn't go down to a lower viscosity as it won't help any in avoiding failures. I would not consider mainstream 5W-30 adequate for these engines

I have an EJ22 which is known for being one of the most reliable Subaru engines. From my experience most Subaru engine failures occur on the EJ25 or other version of the 2.5 Liter platform. Additionally, I talked to a local Subaru engine builder who said he uses 5w30 in all his new engines.

Another thick vs. thin thread with a dose of winter rating on the side.

I apologize if I am reiterating an already dead subject.

However, my question is a little more specific than that - it's about if the winter rating affects the true viscosity or protection of what should still be a "30" grade - and specifically if there's a reason all these old manuals, don't recommend 5w30 but instead recommend 10w30. Is it because the oils back then weren't as good and you needed a 10w30 to not shear down as much, or is it a different reason?

Go to the BITOG homepage and under 'Articles' pull up Motor Oil University.
Remember, the first number is the cold visc. and that is only relevant for a short time from startup to warm. Cold weather you 5 or even 0 visc. so it circulates quickly. At running temp. you want 30 as specified by manufacturer. So simple - use 0w30 or 5w30 winter and 5w30 or 10w30 summer. I have had subarus for a long time (had 1988 GL, then 1995 legacy 2.2, then 2004 impreza ST wagon, now 16 WRX) and I used M1 5w30 and past 10 years M1 0w30. The 0w30 is great for reducing the subaru ticking, sewing machine sound, valves at startup - especially when cold. Your older subarus may benefit too. Be brave and try 0w30 Mobil 1 AFE (walmart $26 for 5qt jug)!

I fully understand the whole winter rating thing, but I appreciate you being willing to kindly educate.

My question / curiousity is mainly why the MANUALS don't follow that logic. If the winter rating truly only matters at cold start (at least with modern oils now), why do/did the manuals recommend 10w30 and specifically say not to use 5w30 over 60*F, or for, in Subaru's case, the vaguely mentioned "high speed driving"?

Again, my only guess is that 'back then', the 10w30s wouldn't shear down/thin out as fast as a 5w30. I fully agree that if both are 30 grades at 100*C, the winter rating should not matter. So why do the manuals say differently?

For what it's worth, I'd be more inclined to experiment with different oils, but every single thing I have runs so darn good on 5w30, even my 22re and my Subaru. They don't tick, slap, vibrate too much, or anything. As far as how smooth they just "feel", I don't think I can get any better. That's a big reason why I'm not sure if I should even change anything. I suppose the next step for me could be a UOA.

Thanks all.