What weight oil for older trucks & SUV's?

When they pass 100,000 miles. Do you guys switch from the factory 5W-30 to like 10W-30 or 10W-40 year round or just swap to it for summer driving? Just not sure 5W-30 is the best for older motors.

Using the high mileage 5W-30 Castrol GTX in our vehicles as they all have over 75,000 miles on them.

My Ramcharger has well over 225,00 miles om it. I use Amsoil 10w30 Signature series oil with no problems....I use Amsoil in all my vehicles, and small engined equipment....

My Ramcharger has about 250,000 miles and now use 15-40 diesel oil. The van about 235,000 miles and use Valvoline 30 wt.

I run 5w30 in the 318, it came out of my 87 Diplomat and is in my 65 Cuda, over 200k miles and great oil pressure.

You need a good oil pressure gauge and use it to monitor your pressure. Do not go thicker than you need for acceptable pressure, any more just wastes gas.

I use diesel 15-40 in my stuff, gas or otherwise, I like the extra sink properties.

Depends on the truck. For the 90's magnum injected stuff and newer, 100,000 miles is not that much. In my 99 2500 with the cummins, I just did the oil change for the winter and run 5w-40 rotella t6 synthetic. Truck has just shy of 240,000 miles on it and hot oil pressure at idle is great. Synthetic 5w-40 is what the owners manual specifies for our winter temps.

The old carbed 4.2 that was(before I yanked it out) in my 88 jeep had low oil pressure. Oil pressure was so low at a warm idle that one lifter would bleed down. Get a little warmer and a second would bleed down. Even in the dead cold of a manitoba winter. Kind of embarrassing at the drive through getting coffee with this thing clacking away like there were elves with hammers inside the engine! Still went 4x4ing with it like that and gave that engine even more abuse. I tried dumping in some thicker oil, it made no difference lifters bled down just like before. After the transmission crapped out I finally pulled that engine!

With you being in the south and not having cold winters like here, I would just run the 10w-30 year round and be done with it.

In my Cherokee with 166,xxx miles I run Rotella 15-40 in summer and winter I run Rotella T-6 5-40 for easy starts.

I've used 10w30 Valvoline in everything I've owned for 24 years and never a problem.

94 Chevy Caprice - 204k+
94 GMC - 196K+
04 Durango - 147k+ (and no broken timing chain yet )


IMO, 5w30 is for better gas mileage. I'll take a few tenth's loss of mileage for the piece of mind.

Castrol Edge synthetic in 5w-40 is the ticket. Has zinc like the diesel oils do and it has a wider viscosity range for year round use. It is also available in 5w-50 if you want some racing oil type characteristics.

In a multi-grade oil the first number is only important for cold starts to reduce engine wear prior to reaching full operating temp. Most people don't realize that even with a 10w or 5w oil you will experience 90% of your engine wear on startup. The oil at those seemingly low viscosities is still FAR too thick to fully lubricate bearings at ambient outside temperatures. Even a 0w oil is too heavy but it beats a 5w or 10w. For an older engine I'd probably look at something like a 5w-30 or 5w-40 type oil. If they offered a 0w-30 or 0w-40 might consider that as well. Even between 30w and 40w oils there is relatively little difference in lubrication qualities and viscosity at 180-200 deg F. Surprisingly, once hot, most quality oils are pretty darn similar. The synthetic blends generally are better flowing at cold temps than dino oils stamped with the same numbers. A 5w-20 synthetic oil might perform more like a 3w-20 when compared to 5w-20 dino oils.

While you might want to raise the hot oil viscosity as the vehicle ages, you don't want to do that with the cold range viscosity. Wouldn't be surprised that in another 5-10 yrs the auto manufacturers are using a 0w-20 or 0w-30 oil in many of their new cars. For the OP's car I'd probably either stick with the 5w-30 or go a bit higher to 5w-40 if that saves on oil usage. Syntec will give you better protection both cold and hot. But I wouldn't go to a 10w-30 as you'll only get more wear, not less. The key has always been getting oil to the bearings as quick as you can for as long as you can as the engine warms up.

Mobil 1 offers a 0w-40 in synthetic and call it European style. I don't think it has any zinc so you wouldn't want to use it in flat tappet cammed motors.

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A 5w-20 synthetic oil might perform more like a 3w-20 when compared to 5w-20 dino oils.

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My car specifies 5w-20. Since I put on a lot of miles between changes and it sees a lot of cold starts and short trips I run amsoil synthetic in it. I will tell you that oil is almost as thin as water even when cold! I'm sure they spec it for fuel mileage. The engine was designed with that in mind so I have no problem with it.