Oil Type Question Moble 1....High Milage

[Bob Dunahugh]

Matt has some great points to think about. Our engines are very dirty engi=
nes. Nothing like the modern ones now. And just need frequent oil changes a=
s compared to newer engines. Some newer style engines use 0-20 oils. Syn's =
are great for these clean engines. With ours. 3,000 miles of use has prett=
y much ended the useful capacity of the oil filter. As at that point. Most =
oil is going to the oil filter bypass valve. Thus very little. If any oil i=
s getting filtered. And the higher the miles on your Olds engine. The even =
shorter the life of your filter. You can reduce oil contamination some by i=
nstalling EFI. The very best thing you can do to extend the life of our eng=
ines. Is simple drain the trash that's built up in our engines at 2500 to 3=
000 miles. Mineral oils can take temps to around 310 degrees as I recall. S=
yn's are higher. So what. Your engine is toast at 250 degrees. Syn's can be=
left in for more miles. But the filter should still be changed at the 2500=
, to 3000 range for our engines. I have a 96 Astro that's coming up on 300,=
000 miles with mineral oils used. And I never have had to add oil between c=
hanges. Would Syn's done better? All oils are to be change once a year. Ho=
w many miles do you put on your GMC each year? Syn's for more modern engine=
s. Have at it. In my GMC. I'll stay with the diesel blended 10W30 with 180=
0 PPM that I use. That's my 2 cents worth. You need to do what feals right =
for you. Bob Dunahugh 78 Royale

 

[Matt Colie]

> Matt has some great points to think about. Our engines are very dirty engines. Nothing like the modern ones now. And just need frequent oil
> changes as compared to newer engines. Some newer style engines use 0-20 oils. Syn's are great for these clean engines. With ours. 3,000 miles of
> use has pretty much ended the useful capacity of the oil filter. As at that point. Most oil is going to the oil filter bypass valve. Thus very
> little. If any oil is getting filtered. And the higher the miles on your Olds engine. The even shorter the life of your filter. You can reduce oil
> contamination some by installing EFI. The very best thing you can do to extend the life of our engines. Is simple drain the trash that's built up in
> our engines at 2500 to 3000 miles.
> Mineral oils can take temps to around 310 degrees as I recall.
> Syn's are higher. So what. Your engine is toast at 250 degrees. Syn's can be left in for more miles. But the filter should still be changed at the
> 2500, to 3000 range for our engines. I have a 96 Astro that's coming up on 300,000 miles with mineral oils used. And I never have had to add oil
> between changes. Would Syn's done better? All oils are to be change once a year. How many miles do you put on your GMC each year? Syn's for more
> modern engines. Have at it. In my GMC. I'll stay with the diesel blended 10W30 with 1800 PPM that I use. That's my 2 cents worth. You need to do
> what feals right for you. Bob Dunahugh 78 Royale

Bob,

That line is slightly in error.
Any and all conventional motor oils disassociate at 305°F. This is not a Time/Temperature effect. When that molecule of oil get heated to 305, it
ceases to be oil.

Problem: Lube oil cools the underside of piston crowns. If the coolant is 250°F and it is a typical pass car (ours are pretty much), that hot oil
will be real close to or over the jacket water and get sprayed under a piston crown. What is the chance that it stays below that 305 number?
That is where the real problem with a 250°F engine arises.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit