Hello everyone! New poster here but have been a lurker for over 2 years. Would like some opinions on oil recommendations. Truck in question and a little history:

1994 Chevrolet 1/2 ton 4x4, 5.7l 350 TBI, 3.73 gears. 240,000 miles. I bought the truck with 98,000 mi back in 2001 from the original owner. He always used Pennzoil 10w-30 and so did I until around 200,000. I've used valvoline, QS, and a few others. Truck does not smoke at all and runs great! It does leak a little and I'm sure it burns some. I use the truck to pull my boat in the summer. I change it once a year since it uses oil, I use a good filter, and I only put 4,000 miles a year.

I was given some castrol syntec 10w-30 and used it for the last OC along with my usual WIX filter. Well I pulled my boat the other day, about 3-400 mi total and was 1qt low. 1qt for 2,000 mi is normal. Granted I was running in 3rd turning 2,600-3,000 RPM, 65-75mph, but that seems excessive.

I am thinking about running a 10w-40 high mileage oil from now on. Does that seem like a good choice. What are some of your thoughts and suggestions? Keep in mind it gets hot here and I am using it for a fair amount of hard towing.

Thanks for your time!

This engine is known to have valve stem seals get leaky. Not saying thats your problem but it does happen often as they get older. The engine is very tolerant to oil viscosities. I agree with you 100 percent that a 10w30 or 10w40 high mileage would be a good try. I have the 4.3 in my 1500 that runs good but burned about a qt per 2 or 3 k miles. I ran a run of M1 10w30 HM and it actually did curb its usage a little bit. Honestly where you are, that thing would handle any HDEO 15w40 just fine. I know a few guys that have run M1 15w50 in those 350s for a long time with no issues. Take the middle ground and run some 10w40HM. I bet it will help your situation. Good luck

Thanks jstutz. I've heard of these engines having valve stem seal leaks. I bet most all that are smokers can be attributed to them, especially the ones that smoke on start up. To their credit there are a lot of these trucks up here where I live and a lot of them are farm trucks(hard use) with 250,000+ miles with no issues of smoking. I have watched the exhaust on start up after the truck has sit for 6+ weeks and there is absolutely no smoke. The rear main seal has leaked since I bought the truck with 98K. I even replaced it myself when I pulled the trans for a rebuild at 160K(radiator leaked coolant into trans cooler line and washed out the clutches) and it still leaked. After driving and parking it, it will leak 5-10 drops. Annoying but I'm fine with it. I honestly think it is burning it 50% via piston rings and leaking the rest. All perfectly fine with me given its age and mileage. What's a good 10w or 15w-40 HM dino oil? Thanks

For your climate, a 15W-40 HDEO would work well.
Might not help with the leak, but it will do a good job protecting the engine.

I would use Mobil 1 high mileage 10w40 or Valvoline Maxlife 10w40.

Thanks guys. The Valvoline looks to be a good affordable oil and WM sells it in big jugs. I would like to stay away from full synthetic for this oil burner. I'd like to hear some more opinions on the HDEO 15w-40's that was recommended.

I think an HDEO 15w-40 would suit you fine. There are all kinds available at reasonable prices. Shell Rotella, Mobil Delvac, and Chevron Delo are usually the top choices. John Deere also sells some excellent HDEOs. I'm partial to Delvac, but that's mostly because it's the easiest thing for me to find. Rotella comes second for me in availability, basically a tie with Delo.

You can probably get it in 4 or 5 quart jugs, and a 5 gallon pail. I believe you can get the Rotella in a 10 quart jug or something like that, too.

A HDEO (either 15w-40 or 10w-30) would work well.

OTOH - I think about any quality PCMO would do well, too.

The key to longevity is not so much the fluid you use (although sticking to spec'd fluids never can hurt), but it is moreso the commitment to fundemenatl maintenance.

http://www.knfilters.com/news/news.aspx?ID=157
http://www.leftlanenews.com/mans-chevy-1200-miles-from-million-mile-mark.html
http:// (google "millionmilechevy" - I won't post the link because it's a competing Amsoil link)
http://millionmileford.com/
http://www.millionmilevan.com/
http://www.autoblog.com/2006/04/03/chrysler-ceo-calls-owner-of-million-mile-dodge-ram/

Many with dino oils, some with synthetics. The one Ford goes 10-20k miles on 10w-40 Valvoline PCMO!

The list goes on and on ...

My point: what fluid you choose pales in comparison to your overall commitment to doing good preventative maintenance.

A '94 TBI 350 should have roller lifters, which would mean that regular SL/SM PCMO would work OK, my brother still drives my old '94 TBI 350 Suburban all the time to tow his Sea-Doos around, and it runs on 20W50 with STP Oil Treatment added (due to low hot oil pressure/worn cam bearings). It's right at 211K, no blowby, wrist pin, nor con rod noise, unfortunately the previous owner(s) were a little lax on oil changes, or it would be better.

Also, it usually burns 1 quart per 1,000 miles on the highway, which is masked by the catalytic converter burning the oil smoke.

Are you regularly replacing the PCV valve? Sometimes when they are clogged it can cause high oil consumption and leaks.

i agree with all of the above, i have 2 292 chevys, i've never seen an older chevy that the valve guides don't weep at least a little.
i run 15w-40 in both of mine, although i'm quite sure 10w-30 would work just as well.

unexplained burn-off is not that uncommon, just keep an eye on it to make sure it doesn't become steady usage

I was just thinking that an actual HM oil couldnt hurt just in case you had some seals drying up somewhere. 15w40 is not a uncommon viscosity to be run in these guys and will hurt absolutely nothing in your temps. With it burning as much oil as it does though it may be a little better to run a HM oil that usually has about 1000ppm ZDDP vs 1200 or 1300 ppm in a HDEO. Might be a little easier on your cat. Most dino HM oils will split the difference and you will get a little better add pack than a standard PCMO with the added viscosity that your after with the added benefit of a heavier dose of seal conditioners. Honestly i have only tried the M1 HM oils and have looked into the Pennzoil HM oils that look pretty good too. Ive been wondering about the QS HM oils lately. I know in the past that had slick 50 in them or something so i have steered clear of them. I have had max life recommended to me a while back by someone on here that appears to really know what he is talking about so maybe give that a shot for a while. If it dont do anything for you throw some rotella or something in there and give that a shot. None of them will hurt you. Youll probably just have to do some experimenting to see what suits your truck the best with your given conditions. Good luck and keep us posted on what worked for you.

Just for fun, throw a few oils in here and i think you will see that running a slightly heavier oil ie. 15w40 or 10w40 in the summer, or winter for that matter, wont hurt anything at all. Keep in mind that the charts become less and less accurate under about 0 degrees.

http://docs.google.com/fileview?id=0B6pX...yMTAw&hl=en

Mine does not, neither does your suburban(hydraulic flat tappet). The block has the provisions for a roller cam but trucks did not get rollers until 96(vortec)