94 LT-1 M1 0-40/0-30 mix 10066 mi @ 216k

[454MAG]

94 Formula Lt1 216,830 on odo. 10066mi on oil in 5 months. 3qts each M1 0-30 and 0-40. this is the thinnest oil this motor has seen since before 100k.
It was run during one of the coldest winters on record for MA.
Oil M1 0-30/0-40 M1 10-30/15-50
Miles on oil___ 10066___ 10122
miles on unit___ 216830___ 206764
date___ 6/7/05___ 1/17/05
Auminum___ 6___ 5
chromium___ 3___ 2
iron___ 36___ 26
copper___ 4___ 4
lead___ 12___ 4
tin___ 3___ 1
moly___ 87___ 54
nickel___ 1___ 2
mang___ 0___ 1
silver___ 0___ 0
ti___ 0___ 0
potassium___ 2___ 0
boron___ 151___ 100
silicon___ 12___ 7
sodium___ 10___ 7
calcium___ 2888___ 2226
magnesium___ 66___ 157
phosphorus___ 895___ 681
zinc___ 1008___ 766

viscosity___ 67.6___ 75.5
flash___ 425___ 410

Blackstone comments

TED: No problems showed up in the second sample from your GM LT-1. All wear continues to read
close enough to averages to be considered normal. This is excellent considering you are running the
oil about 6,500 miles longer than average. The mild increase in iron and lead is probably from
something operation (racing, city driving, etc..) and isn't high enough to call a problem, just something
to monitor. Silicon increased so you may want to look at your air filter. Other than that, things look
pretty good. No fuel dilution or anti-freeze showed up.
my thoughts.
This oil was too thin to protect my bearings from the abuse I give this car. Although it is a 100 mile a day daily driver it still gets drag raced occasionaly and generally beaten on. I am sure the couple of months of 0 degree cold starts did not help the numbers but the 10-30/15-50 mix gave much better numbers. Current fill is M1 TSUV 5-40. Hoping to use this year round.
hot oil pressure is 25 lbs at 550rpm compared to 17lbs with the 0w mix. I like this.
Any Comments from the board would be welcome.
Ted

 

[454MAG]

Forgot to add filter was ac delco pf35l
no oil was added during this entire interval which was very strange. I filled it with 6 Qts and it was just ready to need a qt when I drained it. current filter is a wix.

 

[TooSlick]

As a general rule of thumb, as long as the fluid is thin enough to allow easy starting, it's thin enough to effectively pump throughout the engine. Most of the operational time is spent with everything fully warmed up, So you have to bias the viscosity choice towards that steady state condition.

The 5w-40 will work perfectly in this application - better even than the 10w-30/15w-50 mixture.

 

[454MAG]

After a couple of weeks on the 5-40 I have noticed two things. My motor is quieter and has higher oil pressure especially @ 220-240 deg. My fuel mileage has decreased from 25.2 avg to 24.1. I can determine fuel mileage very accurately because I drive the same 100 miles every day at the same time and speeds. Will this motor go 300k w/o a timing chain ?? It still runs like the day I bought it and has not had the valve covers off yet.
Thanks for the input TOOSlick - I was waiting for the 5-40 to show up locally. I have also used straight 15-50 in the summer w excellent results.

 

[TooSlick]

454MAG,

The relative fuel efficiency of lubricants (using like basestocks), is roughly proportional to the cube root (CR), of 1/high temp-high shear viscosity @ 150C. Note: I derived this relationship from the standard calculation of viscous drag on a boat hull as a function of cruising speed.

In this example:

0w-30/0w-40 mix, HT/HS of approx 3.2 Cp
5w-40, HT/HS of 4.1 Cp

CR of 3.2 = 1.475, 1/1.475 = .68 or 68.0%
CR. of 4.1 = 1.60, 1/1.60 = .625 or 62.5%

The theoretical difference in these two fluids in terms of fuel efficiency (assuming both are 100% shear stable), would therefore be on the order of 5.5% under steady state conditions. However, in practice your average oil temps will run about 5F-10F hotter with the 5w-40 due to increased friction. Hence the difference in operating viscosity and calculated fuel efficiency will be less. The difference of -4.37% with the 5w-40 looks to be about right....

As a final note...a steady state, oil temp difference of +/- 20F is roughly equivalent to going up or down one SAE grade. For example, a midrange 30wt @ 200F, will have about the same effective viscosity as a midrange 40wt @ 220F, or a midrange 50wt @ 240F. This temp/viscosity "equivalency" is a very useful tool when recommending lubricants for different applications....

 

[454MAG]

Tooslick,
Thank you for that detailed explanation. That is the first time I have seen actual calculatiions for viscosity VS fuel mileage. Very nice. Do you think the mix I used was too thin for adequate protection or am I splitting hairs. I would have run straight 0-40 for the winter but could not get enough hence the 0-30 mix. Would you run the 5-40 year round or switch to straight 0-40 for winter ?

Thanks
Ted

 

[TooSlick]

The 0w-40 by itself would not have worked any better than your blend....

The problem w/ most of the M1 formulations (except the 5w-40/15w-50), is additive chemistry and not simply viscosity. This is precisely why many cheap, conventional lubes show significantly lower iron levels, even if they aren't any thicker in terms of HT/HS viscosity.....