sothpaw2

Hi,

I've been running M1 10W40 (the Hi mileage kind w/the extra additives) for a few years now. In 2010 I switched the 10W40 out after the summer but ran in it on the street May-September. Last year I ran the 10W40 all year since I only started the car twice December-February and never below 30F. Just seemed wasteful to go to 30wt for soooo little driving October-April.

Has anyone else done this? Long term...80kmi? Blackstone reports? It dawned on me recently that while I know many run 10W40 or even 15W50, these may well be 90% track cars where mine is 80% street.

Thanks,

Andy

froggy47

Since you say mostly street & live in Maryland, IMO 5w-30 is a better choice. I run 10w-30 but my "coldest" cold start is 70 f in an enclosed garage.

I think an oil that gets to 40w when hot is too thick for a modern tight tolerance engine that's mostly street driven.

I do hpde in socal with 10w-30, the oil gets hot but pressure is good.

sothpaw2

I think 10-w-30 is probably the best choice for combined street/small track use but since I do hit 270(MAX) oil on track w/the oil cooler, I wanted the extra protection from the 10-w-40. Best to get a bigger rad and drag that down to 255(MAX). But until I go that next step...wondering if I really need to go to extra trouble of dumping my 10-w-40 after each event. A bit of trouble but worth it if there were a real benefit.

Viscosity comparison for M1:

10w30 10w40
40C 78 95
100C 12 14.6

c4cruiser

The various car manufacturers spend hundreds of thousands of dollars to test a variety of oil viscosities for the engines that go into their cars to see which one will give the best overall service and protection.

For a street motor, there shouldn't be any real reason to go to a viscosity that it outside the range of a given manufacturer's requirements, especially for an engine that is still under warranty. Back in 2002, I listened to Dave McLellan state that the factory-fill 5W-30 Mobil-1 provides excellent protection for the LT1/LT4 and the (then fairly new) LS1 even when oil temps can approach 300 degrees.

I remember years ago when Chevrolet stated flatly that the use of 10W-40 in any of their SBC motors that were under the factory warranty would be cause for immediate cancellation of that warranty.

hellrazr

There's so much conflicting information in this area, and so many variables that it's hard to know. Press anyone with a strong opinion on the subject, and they usually make authority arguments. Driving schools that maintain track corvettes have some empirical data, but it's for their specific application.

I ran 5-30 per the manufacturers recommendations for a car that was probably about 35% track, 65% street in Southern California. A few times I hit 300+ degrees on-track.

Engine needed rebuild at 55k miles. Hard to know if there is any correlation to the oil weight.

rayk

That's what I see too. I currently run M1 15w-50 because when I was at Spring Mountain, that's what the tech told me they used in the cars. I asked because the oil pressure was above the normal found in the GS.

I'm not comfortable running 5w-30 on the track as my oil pressure really drops when the oil get to around 230-240.

Looking for a good alternative to try keeping in mind I still have the factory cats I don't want to ruin.

cadguymark

there is your correlation

Cobra4B

I used to run the M1 5w40 in my old Z06 all the time... bought the car with 20k on it sold it with 80k on it still making 430+ rwhp with a cam-only swap. In the current racecar I run Amsoil 10w40 all the time.

hellrazr

Oops, you know what I meant

ZedO6

Wrong...CAFE rules all these days. Durability is secondary to fuel mileage. Oil companies are expected to reformulate oils as required for the manufacturers engine configurations driven by fuel mileage.

rayk

Ford went to 5w-20 from 5w-30 just to gain an additional .10 mpg.

Supercharged111

How about at 300*F? They're within 1 cs of each other at that temp.

froggy47

I believe most of the manufacturers will sacrifice an engine or two (very few run them hard) to gain a tenth or two mpg for the fleet.

So for all you guys who get on the soapbox and say "I use what's in the owner's manual, they know best", good luck with that.

ScaryFast

Mobil 1 is factory fill because they pay GM (and others) big bucks to put that sticker on the fill cap so the customer buys that product at every oil change.

Is it good oil? Sure. Do I and most of us here use it? Yup. Is that because my owner's manual recommends it? Nope.

I currently have 15W-50 Castrol in the LS2 street/track car. Not enough miles to tell you that it works for the long haul, but for now my oil pressure is good at ambient, and when the oil hits 300* it's still over 30 psi instead of 18 psi with 10-30.

I have run Mobil 1 10W-30 in the race car for ten years, but that car has oil coolers and keeps pressure with thinner oil. Every Blackstone report over that time has said "engine looks new".

rustyguns

Pumba

From 8 years of LS engine experience in a Corvette and 30+ years of Powertrain experience as an OEM Engineer, I would recommend that you change over to Mobil 1 or Red Line 0W40 oil. To both of these I would add a bottle of ZDDP for increased Zinc and Phospherous.

See the following Blackstone Labs oil analysis:





There isn't a knowledgeable Powertrain Engineer that would recommend a 5W30 oil for an engine if CAFE standards were eliminated.

-

froggy47

What is your response to those that say an oil that goes to 40w hot is too thick for the tight tolerances of modern motors?

In other words there's high pressure, and there's flow, not always the same thing. Your Blackstone says you have both.

rayk

Interesting. I was looking at 0w-40. Where do you buy the additive?

Supercharged111

X2. I did the 0W40 in my truck (which has no cats) so not concerned about ZDDP plugging them up in the next 10 years. How is ZDDP for O2s?

Han Solo

My former DD now autox/track use Mustang and my F150 tow vehicle get 5W20 synthetic blend Motorcraft and both have over 100K on the clock. And this is in FL.

The Mustang use to get 5w30 but developed a slight timing chain noise on start up. After switching to 5w20 the noise all but went away. It only does it after sitting a few weeks now where as it was almost every start up with 5w30. Go Figure?