M1 10w40 High Mileage OK in a 1988 L98 Corvette?

arakele said:
It is weird seeing an antique auto tag on that body style corvette.
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I agree. That car looks ahead of it's time. Beautiful car!!

Oil,I'd start out with a 10W30 in your favorite brand and a classic (non-ecore) AC Delco oil filter. But,10W40 certainly won't cause a bit of harm. Lot's of good 10W40's out there. I ran everything from 10W30-20W50 in my 300ZX. 10W40 was definitely the "sweet spot" in that car. Plus I'm one of BITOG's "thickies":D (I prefer to use the thickest oil allowed per fsm).
 
Congrats on the car. I would lean towards 10w30 HM or 0w40 if you prefer a 40 grade. I would suggest changing all of the fluids if you don't know the maintenance history.
 
'88 was a great year; Chevrolet continued to work out bugs. Which transmission?
As to oil, it's a small block Chevy. I would stick with 5w30, but I doubt your engine will know the difference.
I had an '86 (used) and '90 (new) both Z51 package. I really couldn't afford the '90 and sold it after 1 year.
 
Robvette said:
I just got it, so we’ll see
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Congrats, hope you enjoy it.

Where I was going with the question is that if its still tight and consuming less than a quart every 3-5K Id keep running 30 in it.

If its starting to loosen up and eat a little oil going to a 40 may slow down consumption a bit, but it isnt really going to buy you much more in the way of protection unless you are running the car on a track.

Small block chevies wear out the top end before the bottom and its common to need a valve job as they age, but 100K isnt high mileage.

Modern 40's aren't going to cause any problem, but it will be a bit harder to pump and if you dont have to there isnt much point.
 
Robvette said:
Just purchased this beauty and the manual calls for 5w30 but this engine has 95,000 miles on it and it's 32 years old and I've had nothing but good luck with M1 High Mileage 10w40 in my other old and high mileage cars. Any reason not to run 10w40 vs 5w30? Thanks!
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Absolutely NO on the 10w40. GM engine of that period and later enjoy a good 5W30. All you will do is loose HP, cooling ability and change the bleed-down rate of the hydraulic roller lifters which will cost you bottom end torque.

That TPI L98 is understressed but provides a satisfying low and mid range torque that Gen I SBC are famous for. Don't mess that up!

- Ken
 
350Rocket said:
That is true, there was a tsb I saw with my own eyes, but like you said has no bearing on today. They sludged up more because of lots of VII.

I would run m1 0w40 personally but the 10w40 high mileage is fine t
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Robvette said:
I just bought the car, and it runs really well. My understanding is that 30 weight oils were often specified to help meet fleet fuel economy targets - not for performance or engine longevity.
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Yes they were, I took continuing education classes in the Automotive department as Skyline Jr college There was a GM person teaching some of the classes during the time I went there. Emissions and CAFE were the driving force in design.
 
UncleDave said:
Congrats, hope you enjoy it.

Where I was going with the question is that if its still tight and consuming less than a quart every 3-5K Id keep running 30 in it.

If its starting to loosen up and eat a little oil going to a 40 may slow down consumption a bit, but it isnt really going to buy you much more in the way of protection unless you are running the car on a track.

Small block chevies wear out the top end before the bottom and its common to need a valve job as they age, but 100K isnt high mileage.

Modern 40's aren't going to cause any problem, but it will be a bit harder to pump and if you dont have to there isnt much point.
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Agreed on the top end. My Caprice had 240k miles and it was prematurely wearing out the valve seals (did them 10 years ago and it needed them again - I put a new catalytic converter on to hide the blue puff).

Despite that it only used about a qt every 2500 miles. Summer time I'd prefer a 40 weight in it but winter was when it got most of its usage and I ran 0w30 or 5w30 full synthetic and it didn't seem to know the difference.
 
M1 5w30 of any special blend will work fine in your L98. GM went to roller lifters in that engine in 1987, so there is no need to fret over cam lobe and lifter wear. It's reasonable to go to the High Mileage blend because your car has over 75,000 miles and may need some seal conditioning. Chevy never specified 40 weight oil for their small blocks, even before CAFE standards.
 
Slightly off-topic...

Not sure if you have the space and/or ground clearance, but RA has the Fram FPS5 on close out for $3.05. This is the shop version of the Ultra XG5 without the textured grip.
 
A_Harman said:
M1 5w30 of any special blend will work fine in your L98. GM went to roller lifters in that engine in 1987, so there is no need to fret over cam lobe and lifter wear. It's reasonable to go to the High Mileage blend because your car has over 75,000 miles and may need some seal conditioning. Chevy never specified 40 weight oil for their small blocks, even before CAFE standards.
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However it was always specified in the owners manual for certain temperature ranges. See attached the original oil cap on my 83 Caprice. That's the oil grade it tells you to use. Since it doesn't say, I assume they expected you to look in the manual and choose wisely based on ambient temperature range? See the tip of the zip tie pointing to the cap lol. Sorry, I normally trim my zip ties but didn't that day.
 

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There is no reason to run a "real" 40 grade in this engine unless it really consumes a lot of oil. A Euro 40 grade or the HM 30 grade will be a better choice.
 
Considering that the engine runs good, you're overthinking the oil selection. I understand the concern about lower viscosities and CAFE requirements, but 30 grade provides great protection and is not a light viscosity. For "energy conserving" oils, 0w20 and 5w20 are the main concerns and I would never run them in a SBC of this era. If oil pressure is good and you're not burning oil, 10w40 may be too heavy. I still suggest 10w30 if your winter ambient temps stay above 10F.
 
Jimmy_Russells said:
There is no reason to run a "real" 40 grade in this engine unless it really consumes a lot of oil. A Euro 40 grade or the HM 30 grade will be a better choice.
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Lots of people keep saying this, but none of us have asked the most important question yet ..how does he plan to drive this thing? If it's just going to cruise around and briefly hit 5000 rpm once in a while, then a 5w30 will be absolutely fine. If he's planning on driving the snot out of it, a euro 40 grade would be a good choice. Personally the only 40 grades I've been using in either of my old V8s or my "modern" gm LS V8 is a euro 0w40.

My Caprice was happy on 30 weights other than a little oil leaking and minor consumption, but when I towed a large tent trailer up the steepest hill in our area, wide open throttle from the bottom to the top (maybe a couple of minutes sustained wide open throttle) it could probably have used a 40 weight.

The new owner was LS swapping it and said "if it blows it blows". It didn't seem like anything was going to blow it, short of draining the fluids.
 
It's a TPI engine that doesn't really rev much over 5200 or so. Even if he is tracking the car (road course, not drag racing) the oils I mentioned would be more than adequate up to about 250 degrees oil temp. Any more than that he could go into a proper racing 40 grade like Redline or something similar.

With that said I would be surprised if this car ever got into that type of situation.
 
I would extrude hone the TPI runners for increased airflow.

Oh wait, you were asking about oil? 10w30 HM should be good. 10w40 unnecessary.
 
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