10w-40 OIL?

[glyanez]

Any one ever use 10-40 oil in their older caddy's. The manual recommends 10-30, but have heard of people putting 40w in their older cars, especially in stop and go driving.

My 97 seville sls ( 94k ) is primarly used for city driving, and was wondering what oil to put in next time i change the oil. Should i go with an HD formula?


gee05

[Ranger]

10W30. HD if you feel the need.

[submariner409]

A 97 SLS with 94k is not "an older car". While 10W-30 oil in a SL - SM designator is the latest and greatest, you could also use a 10W-30 "Truck and SUV" or "Long Life" oil, which carries a somewhat heavier additive package. 10W-40 and 15W-40 is getting into the realm of light duty diesel and large truck work.

The "High Mileage" oils have an additive designed to swell seals and oil-contact gaskets, probably not a good idea in an otherwise tight engine.

My Ford F150 4x4 with the 4.6l SOHC engine uses 5W-20, and at 55,000 miles uses not one drop of oil between 7,500 mile changes.

[Talamant3z]

i use 10-40 in my eldorado it gets very hot here and in the summer my car will say "low oil pressure" when i use 10w-30

[98eldorado-lee]

Originally Posted by Talamant3z

i use 10-40 in my eldorado it gets very hot here and in the summer my car will say "low oil pressure" when i use 10w-30

I used high mileage 10-40 last time I changed my oil; I live in florida; but I think next time I will use high mileage 10-30(why, just because thats what the manual calls for), also I would not use synthetic in a high mileage motor. (its too thin) the manual calls for (0 to 100 degrees ,use 10w 30) (60 and anything below, use 5w30) take your pick.

[Krashed989]

I use high mileage 10w-40 in my engine because I have over 140k miles on her. My thought is that with all those miles, the main bearings and whatnot probably have bigger gaps which means less oil pressure upstairs in the heads. Plus I have an oil leak and it slows it a tad.... However, 10w-40 is NOT recommended in any automotive engine because after the additives wear out it gets gummy and leaves gunk in the engine, or so I've read.

[mtflight]

The 93-99 northstar engine (L37, LD8), which was designed when motor oil had a significantly higher amount of ZDDP (an anti-wear agent for metal-to-metal contact), has sliding, direct-acting followers in the overhead cam. This translates to over double the friction in the valvetrain (measured in ft-lb), when compared to the 2000+ version (which has roller finger followers) at most any point in the RPM range except at close to redline when the gap narrows but remains about 30%.

Some diesel oils have had significantly higher ZDDP than standard motor oils, but the latest version have less. Do a search on ZDDP and you will find a handful of posts, some of which got quite heated.

In a nutshell, one side of the camp presents evidence that there have been a lot of flat tappet failures. Another side says oil is oil is oil. Someone reputable and very knowledgeable said using the 15w-40 Rotella oil would not harm it, and that's what I ran on my L37 1998 Eldorado for many thousands of miles without signs of engine wear. Apparently the viscosity modifiers of old, used to gel up, but current versions have synthetic additives that don't do this anymore.

[Ranger]

Apparently the viscosity modifiers of old, used to gel up

Oh boy, did they ever. It was the reason I used straight weights for the longest time. I still can see what the old 10W40 did to my dads motor, and it had regular 3K oil changes. When I opened it up, it looked like it had never seen an oil change in it's life. It looked like it was stuffed full of pudding. What a mess.

[glyanez]

Thanks for all the details , sub. True, it is a tight engine, runs like new. Just a habit for me to always look at the years.

10-30 it is.

gl

[Tommy Deville]

Originally Posted by mtflight

The 93-99 northstar engine (L37, LD8), which was designed when motor oil had a significantly higher amount of ZDDP (an anti-wear agent for metal-to-metal contact), has sliding, direct-acting followers in the overhead cam. This translates to over double the friction in the valvetrain (measured in ft-lb), when compared to the 2000+ version (which has roller finger followers) at most any point in the RPM range except at close to redline when the gap narrows but remains about 30%.

Some diesel oils have had significantly higher ZDDP than standard motor oils, but the latest version have less. Do a search on ZDDP and you will find a handful of posts, some of which got quite heated.

In a nutshell, one side of the camp presents evidence that there have been a lot of flat tappet failures. Another side says oil is oil is oil. Someone reputable and very knowledgeable said using the 15w-40 Rotella oil would not harm it, and that's what I ran on my L37 1998 Eldorado for many thousands of miles without signs of engine wear. Apparently the viscosity modifiers of old, used to gel up, but current versions have synthetic additives that don't do this anymore.

I put Rotella or what ever type of Diesel grade oil I may be running in My Freightliners in my cars too when I'm down a quart or two. I've never had a prolbem, been doing it for years.