A recent GM safety recall addressing potential manufacturing defects impacting the naturally aspirated 6.2L V8 L87 gasoline engine dictates that certain engines should now use 0W-40 oil, rather than 0W-20 oil. It’s led owners to wonder whether they should follow the 0W-40 oil recommendation, even if their L87 V8 is outside of the recall window from the 2021-2024 model years. Let’s get into how these oil viscosity ratings work and why GM is using thicker oil in recalled engines.
For starters, whether a recalled truck or SUV with an L87 under the hood gets 0W-40 oil depends on whether it needs to be replaced. If it’s determined that the engine needs to be replaced after failing an inspection, the new engine uses the original 0W-20 oil recommendation. If it passes inspection and isn’t replaced, then it uses 0W-40 oil with the Dexos R certification, which is normally intended for performance cars like the C8 Corvette Z06.
A low number means low viscosity (thin), and a high number means high viscosity (thick). Therefore, the 0W-40 oil that GM is using and recommending in non-replaced L87 engines affected by the recall is thicker than the 0W-20 oil originally recommended.
GM’s goal in using a thicker oil in the L87 engine is an effort to increase the Hersey number so the engine spends more time in the hydrodynamic lubrication phase of the Stribeck curve (a deeper dive into those engineering concepts can be found here). To put it more simply, thicker oil should optimize the engine’s lubrication and prevent catastrophic failure.
However, the thicker oil can create a small but measurable decrease in fuel efficiency because of increased internal friction. Thicker, stickier oil creates drag, which means it has to work a little harder just to operate normally. 0W-20 and 0W-40 oils have the same thickness when they’re cold, but 0W-40 is thicker at operating temperature, which means L87 owners could notice a small fuel economy hit. A recently filed lawsuit against GM claims that owners will be buying hundreds more gallons of gas than they normally would because of the recall.
At the end of the day, it’s best to use the oil viscosity recommended by the engine’s manufacturer. If you have a truck or SUV with an L87 engine and it wasn’t part of the recall (model years 2019, 2020, and 2025), keep using the originally recommended 0W-20 oil. If you have one of the recalled vehicles that passed the inspection, and a GM technician slapped on a new oil cap that says “0W-40,” then continue using 0W-40 for the life of the engine. Sticking with the manufacturer’s recommendation is the surest way to avoid voiding your warranty and, hopefully, to extend the life of the engine.
Comments
There is a lot of misunderstanding about oil viscosity and engines. For example GM itself has said that they designed their L3B turbo 2.7 inline 4 to run on 0w20 and then switched to 5w30 at the last minute for “added protection”. The thinner the oil, the more precise the machining on engine components needs to be in order to keep the rotating assembly in the hydro dynamic lubrication range the majority of the time. Using thicker oil then manufacturers recommend isn’t going to cause problems (within reason) so not switching from a 0w20 to a 15w50. I wouldn’t hesitate to run 0w30, 5w30, 0w40, or 5w40 in these engines.
The primary goal of the lubrication change is to mask defects until they get past the extended warranty coverage.
I believe you are correct. And I thought I read an article that said the NHTSA said no to the Oil change solution, but I can not find it again.
You can’t find it again because GM lawyers said to take it down from all sources.
LM4….My Dad told me when my old Ford I had in High School Got to knocking around he said “Son go buy the highest weight oil you can get. That will get you by for a while.”
Is GM going to pay for the extra cost of using 0W40 oil, its going to cost a lot more for owners to use the 0W40 oil , they will be paying $ 200. + for oil changes now
How many times do we have to say on these poorly published articles, the Corvette C8 Z06 does not use 0W-40 oil. The C8 corvette Z06 uses a 5W-50 oil.
Who said anything the Z06? Only the supercharged Camaro and Corvette from the late teens require Mobil 1 Supercar 0w40. This is more than a viscosity increase, this is racing oil.
Not to fall into the dirty laundry rabbit hole concerning the L87. i myself could care less about using 0w20. for fuel economy but more on longevity of the engine ! 0w20 will not protect eng wear as say 5w30 ! factor in owner neglect and extended OCI’s I would be more of a problem ! just my point of view !
Blame the low quality materials and manufacturing on the oil .
No one will suspect a thing …
You can’t make this stuff up.
btw, keep up the good work, Mary .
Anyone who believes changing from O-20 to 0-40 in a big V8 is going to have a noticeable effect on your mileage is a really dim light on the Christmas Tree .
Funny how the more GM outsources over the years, the more quality goes in the toilet.
Just a coincidence, I guess .
It will. Over a 200k vehicle fleet which is how GM and the EPA calculate fuel economy numbers. But will have no discernible difference for the average driver
I’m not sure that I’d run the 0w-20 in my engine, particularly if I was towing or the truck was going to be subjected to high ambient temperatures. As for running the 0w-40 Dexos R formulation, that’s probably what should have come from the factory. GM has demonstrated that they aren’t capable of reliably building a motor to the tolerances required to operate successfully with 0w-20. Once again the quest for CAFE numbers has caused problems for owners, a la AFM.
GM wants to cover up the problem with engineering gobbledegook. Just say it was piss poor manufacturing and that heavier oil is just a bandaid that costs us more. I traded my 24 in for a 25 so I didn’t spend my life at the dealership like I did with the 8 speed transmission. If Ford had a V-8 in the King Ranch, I would have one in my garage.
My brother bought the Ford,nothing but transmission problems,dumped it when the warranty ran out.
Well,the new 10-spd trans in the GM and Ford half tons and SUV’s are the same. They jointly produce the transmission in a partnership.
Thin oils are just a ploy to eke out a couple additional tenths of mpg on the EPA test. It’s bad enough on a NA motor, add a Turbo or Supercharger and its a early death sentence. Plus, extended oil change intervals and the confusion around Synthetic, Semi-Synthetic and regular Dino oil adds to the confusion. I’ve had both the Ford dealer and a Zippy Lube use he wrong oil (weight and type) in my Turbo Focus ST that requires 5w-30 and says so right on the filler cap. But the dolts that do this kind of work have zero idea what that means, see the lighter oil used in everything else and plow right on ahead. I made both of them drain the crankcase, replace the filter and the oil with the correct product. Do that a few times and the dead engines will continue to expand.
Engine crankshaft main and rod bearing/journal clearances are correlated to oil viscosity. Let’s say the machined clearance is .0015 to .0025 inch tolerance versus .0020 to .0030 inch tolerance. The latter being larger would benefit from higher viscosity oil such as 0w-40. Conversely the smaller the machined oil clearance the lower the viscosity i.e. 0w-20.
But you don’t know that until you pull your crankshaft because GM’s assembly/machining process is apparently not good enough to guarantee that they can build to a tolerance that will allow 0w-20 oil to function successfully.
Seems to me the recall is due to A) bad rods, and / or B) out of spec crankshaft journals. These are both outsourced parts, one from Mexico, one from a domestic supplier. In both cases, it would appear GM’s engine assembly plants did not detect the incoming defects and assembled the engines with defective components. Trying to prevent the damage these defects can cause with better lubrications might be logical, but I will still be driving an engine with possibly defective parts. I would want them replaced.
Gee,GM transmission problems because of fluid issues. Now engine problems because of oil issues. Who does GM use for factory fill? Mobil? ‘Nuf said.
No one is suggesting the problem is due oil at all. The defect has been detected and corrected, but defective parts may now remain in some 600,000 engines.
The are only talking about oil to prevent the damage these defective parts may cause, AND, Mobil 0W-40 Supercar will be an approved oil. “Nuf said?”
First thing I would do when I got my truck home is drain the oil change to 20W40 or 20W50 conventional oil we all used in our engines for decades!!! Our engines regularly went 100,000 miles easy!!
0W 20 or 5W 50. Only dumb people run oil that light. You want 400K then at 5K you put 10W 30, at 50K you ADD Lucas Oil Stabilizer to raise it to 15W 50. Every Start minimum 40 seconds unless Cold Start then longer. MAXIMUM PROTECTION!
GM = Gross Mismanagement
The whole purpose of all manufactures using thin weight oil is so they that extra 1/8 of a MPG for their CAFE rating on the fuel economy. The thinner the oil the less restriction on the engine, but not necessarily better for the longevity on an engine.
You would never want to use a 20W- 40 in an engine designed around a “0W” oil. The bearing surfaces in these engines is harder, and the clearances tighter. The “W” viscosity is the cold-temperature (start-up) viscosity. Using an oil that is heavier at start-up can deprive these engine of critical lubrication. Moving from a 0W-20 to a 0W-30, or 40, is safe – it provides the same start-up protection, and better film strength at operating temperatures. This is what GM is aiming for by the proposed switch. There will be a loss in fuel economy, but not something an individual would notice, Picking up a 1% gain in mpg for 600,000 engines does help GM meet their CAFE requirements, however.
Beware Class Action Lawsuits
Possible Outcome: Plaintiffs convince the judge that 0W-40 oil reduces fuel economy by 1%. An example is 15,000 mi/year, $3.80 per gal fuel, and 20mpg reduced to 19.80. Net annual cost $29.00. Multiply by 10 years and 600,000 engines, and the lawsuit value is some $180 Million. They settle for $100MM, the law firm takes $50MM, leaving each owner with 83 dollars, likely in the form of a discount coupon off our next GM purchase.
No dealer is addressing the recall because the “remedy is not yet available” You cannot get a dealer to do anything with this recall. You can ask them to switch the oil type independent of the recall but the recall will remain open. They will not inspect your engine and tell you if it needs to be replaced. This article is ridiculous because no one has been able to have a vehicle that’s “passed the inspection” because no one’s going to do the inspection for the recall. Also, GM was told to stop doing the oil switch, it’s not the fix for this recall.
It seems the dealers must know something, because there are lately “certified pre-owned” 2021- 2024 vehicles now being released for sale. Somehow these cars have cleared the “stop sale” that the recall placed on them. These vehicles somehow either passed a test or got new engines. I guess if I were a dealer, I’d be sure that GM clears my floor-stock first, before I start a backlog of customer vehicles.
Shouldn’t we hear something soon? I thought the customer notifications were to start in June?
I have a L87 in my 2024 Silverado..due for an oil change ..i was waiting for the recall nothing as yet ..when i change i will go to Ow-40..cause i want to help fix the problem.as long as the dealership is aware..i can,t see why preventive is not relevant..