Chevy & GMC Vans

I was wondering what everyone thinks about the grade of oil that should be used. The recommended weight for my 91 AWD Astro is 10W30, but Im using 10W40 non synthetic. Any issues with using a different weight? Can I use synthetic 10W30? I have 75k on my van, and Ive heard that If I use synthetic on older, higher mileage van, the engine will be damaged because of the thinness of the synthetic. Any thoughts?

What do you think?

Thanks all!

Peppy!

Synthetic oil is as good as engine protection gets for most of us. I use it in my 85,000 mile '98 Astro, my riding lawnmower, my Harley-Davidson and my wife's Hemi Magnum, even my lawn edger! Use it without reservation. Mostly it's available in 5w30-5w40 or similar, I use 5 or 10w40, or you can go back to the 5w30, but I think it's too light for our hot summers in the south. Pick your brand, they're all good!

I'm using Mobil 1 Synthetic 5W30 in Green (over double your mileage), Grumpy has been getting it added as needed to keep up with the oil cooler line leak.

I use mobil1 5w30 synth on my 98 and i'm over 298k kms we used 10w30 convential on my old mans 95 and it's at 290k. i don't know of or have ever seen any problem with running 10w30 synth on 91's

Castrol Syntech. 10w-30 here. As Joe mentioend,,all good.

In my '90 I've been using GTX 20w50 for a long time.
At last count I was installing a quart every 200 miles (321.8688 Canadian).

For the most in-depth info on oil and filters, go to:
bitog.com

I've read some very interesting papers on oil and viscosity.

I like the 20W50 as well. But then, it gets hot down here. I've read the write ups on filters as well, and the more I think about it I may just go back to fram filters. For one they are about 1/3 the cost of the mobile 1 filters. For two, I ran them in my (until I read that danged paper) my jeep, which has 187K miles on it. The $6 difference will buy me 1 1/2 quarts of oil ( I..can't...believe...I'm....typing...this yikes!)
I change the oil every 3000 miles.
Waterboy, don't you have some ridiculous amount of mileage on your van, like 300K or something? And didn't you clock most of that mileage on fram filters? personally I'm going to quit splitting hairs and start buying the fram filters for 3-4 bucks again.
I have this sneaking suspicion that the difference in performance between the various filters is very small. (assuming oil changes are done on a regular basis).

15w-40 Shell Rotella. Been used in the van 11 years/180,000 miles (total miles 272k). There is no sludge buildup in my motor, I assume it is because of the high detergant level in the oil.

As for the fram being less expensive, at my local Wally World AcDelco is less than fram.

yay ac is cheaper than fram at wal-mart.

In the Safari, I've been running Penzoil 5W30 in the winter & 10W30 in the summer months for over 200K miles now. AC or Purolator filters for the most part. No problems.

All my other vehicles run Mobil 1 with either M1 or Purolator Pure One filters.

I use valvoline syntech 5w-30 in my van. it has over 150k miles. I'm switching to mobil1 on the next oil change. I havent driven my van much lately and so it hasnt needed an oil change since january.

15w-40 Shell Rotella. Been used in the van 11 years/180,000 miles (total miles 272k). There is no sludge buildup in my motor, I assume it is because of the high detergant level in the oil.

A good oil for sure and have used it but it and a few others were the last to contain higher levels of zinc sulphat. Something that was removed from regular oil a few years ago. That is Rotella for diesel engines and was recommended for new gas engine break in. Last I read, the zinc content was being reduced in diesel engine oils and has reduced total miles before rebuilds in the fleet of the trucking company I work for. The story also mentioned the zinc would soon be eliminated as regular highway oils and only a few other racing oils would contain the high levels. The zince is what has been the major additive that has kept your motor going as long as it has. I first found out about the higher levels of zinc content in dielsel oils about 10 years ago while riding with a freind of mine in his pick up. I knew he had this truck for years and just happened to ask him how many miles he had on it. He said over 300,000 (350 Chevy) and never had a valve cover removed or anything internal replaced and that he had run it through his trucking companies shop for all his oil changes and ran nothing but Rotella diesel truck oil. I thought it was probably just a one in a million and the story off until I read an article on oil and and zinc sulphat content a few years ago. By the time of this post I'm not sure where the levels are in diesel oil but know it has been reduced or eliminated so you may find you've lost a friend in Rotella use.

yeah, about the only high zinc oil you can buy any more is the Valvoline Racing motor oil that has "NOT STREET LEGAL" printed on it in big letters. Pretty spendy too. Part of the reason for the Rotella reformulation is that they are putting catalytic converters on diesel trucks these days and ZDDP contaminates them. That was the reason it was removed from cars, besides them going roller lifter. I'm still a fan of the stuff, I used to run Castrol but my valve seals are shot and it seems to make my smoking worse at start up. There shouldn't be any problem running synthetic but supposedly it can seep worse if you have an oil leak, so that's something to watch out for.

ED:this stuff
http://www.valvoline.com/pages/products ... product=95