need help with oil choice

[JHZR2]

Hi,

I have three cars, an 83 MB 300D turbodiesel (194k) a 91 BMW 318i (79K) and a 98 Chevy S-10 ZR2 (33k). The benz and BMW both take 15w-40 diesel-type oils (rotella T, Delo 400, Delvac 1300), except in the cold of winter when I drop in a synthetic diesel oil (rotella T in the BMW, Delvac 1 in the MB). The truck is reccomended to use a 5w-30 oil, and when I have used it daily in the summers, I have used either pennzoil or castrol gtx inthe correct grade.

However, I really use the MB for long trips, and the bmw for short ones, as both give much better MPGs. I love the truck, and use it for off-roading, and only on trips where Ill be going more than 15 miles (dont want to give it unnecessary wear). This means that the truck will be sitting usually 4-5 days straight without being started, then driven 15-30 miles generally, then sit for a while again. I liek the idea of a synth oil, as it should stay on the parts longer, and flow easier at startup. I also am an avid user of diesel oils, because of their morew robust additive package and stability, which I feel is needed when the truck sits for days, then is run, then sits again. Lately I have been using Rotella T 5w-40 synthetic. I have noticed a drop in MPG, though, with this oil, due I guess to the higher top viscosity. I am also concerned with the chance of heavy use of VIs, despite being synthetic, which may gum up my engine.

So, I would liek to know, can using a heavier oil (the 40 part) do any damage to my engine? I dont care so much about low MPG, and perhaps a bit less power as I do about wear. the 40 wt oil should protect things better, right? Also, say I was to go with an auto synthetic, like mobil1, can I feel secure that the additive package is robust and good enough (I know mobil 1 has a really good additive pkg, but the way the truck sits I can only guess is hard on the oil to keep condensation, etc under control) to fully protect my engine against the things it might encounted from the usage characteristics it undergoes?

Any reason why not to use the rotella 5w-40 (my truck doesnt reccomend ILSAC graded oils, so cat poisoning isnt an issue), or any reason why I ought to use a 5w-30 synth instead, like mobil 1?

I dontcare about keeping many different types of oil, etc., I just want to do whats best for my truck.

Thanks for your time and help,

JMH

 

[Al]

Personally I have no problem with the 5W-40 being as you live in a milder climate. Mobil 10W-30 though could be just as good choice especially for non Summer. If you are curious you could do an oil analysis to compare the two. If you go with the 40 wt. perhaps you should go with the K&N oil filter for supposed higher capacity-especially during 40 wt. oil during winter usage.

to the boards!!

 

[G-MAN]

quote:

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Originally posted by JHZR2:
Lately I have been using Rotella T 5w-40 synthetic. I have noticed a drop in MPG, though, with this oil, due I guess to the higher top viscosity. I am also concerned with the chance of heavy use of VIs, despite being synthetic, which may gum up my engine.

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I switched from Mobil 1 5w30 to Rotella T Synthetic 5w40 in my Olds mini van about three months ago, and in both city driving and on two 1000+ mile trips, I've not seen any decrease in gas mileage. In fact, on the trip up north last month, the van got the best mileage it's ever gotten: 30.1 mpg average for the 388 miles up there. Average on the way back was 29.7.

Before switching to Rotella T Syn I e-mailed a Shell engineer and asked him about the VI improver used in it. It's common knowledge that Shell makes one of the most shear stable VI improvers on the market, and it's so effective that very little of it is needed even in the conventional Rotella T 15w40. Because of the naturally high VI of the XHVI base oil (>140), even less is needed in the Rotella Syn.

I'm planning to switch my 300M from Mobil 1 to Rotella T Syn at the next oil change. Problem is, it's selling so fast at Wal-Mart they can't keep in on the shelf. I've visited all three of my local Wal-Marts in the past two days and none of them had the gallon jugs and the combined total quart bottles from the three stores was 8.