Quality engine, tranny, and gear oils

[Kenneth]

I have a 94 6.5 turbo with 152K miles. I currently run dela 400 engine and I don't know what's in the tranny or rear end. I got a hold of this truck from my brother last summer who had it for about 4 years prior to my grandpa purchasing it new from the dealer in 93.

My question is, as I am trying to play catch up on the tranny and rear end (my brother never touched them, and don't know if my grandpa had them changed) what brand or type of oil should I use for each. I have been thinking of using a syn but am questioning that since I have read about oil leaks getting worse with the use of syn. I currently have a few leaks, the turbo, valve covers, oil cooler lines next to the oil filter, and possibly a rear main. These leaks are very minor and the truck has been using less than 1 qt for every 4-5k miles. Every time I park the truck i get about 3 small spots of oil less than the size of a dime. The leaks aren't bad, but i am worried if I switch to a syn the leaks will get bad.

Anyway, what reccommendations do you guys have for oil type (dino or syn) and brand (mobile 1, rotella, dela 400, or other brand) and oil filters (wix, ac delco, napa, etc)?

[More Power]

For the time being I recommend synthetic motor oil for just two reasons:

1- Cold weather starting.
2- Those owners who work their diesel engines hard in the hot summer heat.

It's common knowledge that synthetic oil flows better at very low temperatures. A conventional petroleum based motor oil that allows normal diesel engine starting at -20°F won't provide enough engine protection when worked hard at a high engine temperature. Synthetic on the other hand has the ability to flow extremely well at low temps yet provide more than adequate lubrication protection at very high engine temperatures. Since the starting ability depends on a good cranking speed, synthetics make sense during the winter months.

We also know that very high engine temperatures can cause conventional oil to breakdown and lose some of lubrication qualities we need most at those high temperatures. If you pull with your truck in high ambient temperatures, you should consider a synthetic. Turbos will add about 80°F to the oil passing through the turbine bearing housing. A synthetic will help prevent "coking" and may extend the life of your turbo as well. Additionally, a hot shut-down and its effect on the turbo is less of a concern with synthetic oil.

In my case, I'm more interested in the cold weather performance and expect one oil change utilizing synthetic to get me through the cold months of winter. The additional cost of synthetic can be justified here in Montana.

If you change your oil at home using synthetic oil like Amsoil 15W-40, Mobil Delvac 1 15W-40 or Royal Purple, you'll likely pay about the same as if you visited a high volume lube center and had someone else change your oil using a petroleum product.

GM requires a synthetic 75W-90 lube in both the front and rear differentials in those 2500/3500 trucks produced since 2001. It would make sense to use it in all earlier GM diesel pickups. The transfer case requires about 2 quarts of ATF. Because the Transfer case fluid isn't changed often, it would make sense to use synthetic ATF in the transfer case. The transmission ATF is a toss up. A hard working 4L80-E behind a 6.5 should have its ATF replaced every 25,000 miles. Unless you're seeing high ATF temperatures due to towing, a conventional ATF would be fine.

I use ACDelco filters...

Jim

[Kenneth]

Thanks for the input. I currently live in CA and don't see cold weather at all. However, I will be up in Rexburg, ID from Jan-April and the temp is usually around 10 degrees from about Jan- Mid Feb. I had it up there with me last winter and plugged it in everynight. I did replace the glow plugs this summer with Bosch glow plugs from Heath Diesel.

My question is about the oil, I have heard that switching brands of oil can be bad because different brands use different detergents/chemicals and the contrasting detergents/chemicals may cancel each other out and the oil may not be as effective. If I do switch to a synthetic for my winter oil change do I need to stick with a Chevron syn or is it fine to go with another brand syn and then switch back to Dela 400 for the rest of the year? Shell and Mobil 1 synthetics are readily available, but the Chevron syn I would have to search around for. Thanks again for the input.