LS1transam99

Hey guys, is it safe to use Synthetic motor oil on a high mileage LS1, in the 80,000mi range? Or should i go with regular oil, i just got the car and im sure synthetic was never used. Thanks

95GRNZ

FWIW, I started using synthetic in my LT1 @ about 75K miles without any problems. I don't see why LS1 would be any different. As long as the engine is otherwise in good shape.

I, personally, wouldn't hesitate to do it.

TS

Jay3274bbl

Yep, I've been using it for about 50,000 miles with no issues (I have about 84,000 miles on the car).

robb4964

The camaro in sig has over 198k on it and it dont smoke ro anything and is one of the strongest LT1's , even at 197k , I have ever drove/ridden in for the little bit thats done to it.
I think it is becasue of the fact that nothing but synthetic oil has been ran thrue it since it was new.
The LS1 now has almost 130k and still runs perfect and has nothing but syntec in it. Both cars get beat BADLY when driven.

I wouldnt put anything else in a high performance engine.

Greed4Speed

I'd run some seafoam through it first just to clean it out. If you see leakage (which I doubt) or use more oil than you'd like (which was my case) just change back.

I'm personally running conventional oil because my car consumed 1qt of oil with the synth by 3k miles and doesn't with conventional. Sorry, but I'd rather run conventional oil than have fouled plugs, cats, and O2 sensors.

An engine will last as long with conventional oil. The million mile GM pickup ran nothing but conventional oil. Its all in how you take care of and drive your car. I'm not saying synth is bad, it just isn't the sole reason why these engines are seeing so many miles. I've seen guys that ran nothing buy synth have to tear down early. The oil isn't the reason for that either. Look at all the imports that get over 200k miles and have done nothing but the basic maintenance that are running conventional oil. No these aren't "performance" engines, but I've seen them get VERY abused and still keep going.

Run any good oil and a good filter, change regularly, don't drive like a dumb a$$ and you'll be fine.

MarineReconZ28

My 95 had a little "moisture" on the bottom of the oil pan when I bought it, but when I started using synthetic it became small puddles on the driveway. I had 110k miles on it when I put synthetic in it though, so I knew I was taking a chance with it. I'll probably abandon the synthetic next time it's due and see what happens.

PJS TOY

Mark, if you have a way to trace it, try to find out if your intake manifold gasket has ever been changed. There was a TSB out for them, but since you are no longer under the factory warranty, it won't be a free fix. I know that they never fixed it in production, because my 97 leaked. It was just like you said, a little moisture on the bottom of the pan. If I missed one time of cleaning it when I washed the car, it was a mess. They fix it by putting in a new gasket for the head contact area, but use RTV on the ends against the block. Had to take mine back because they did it wrong.

About synthetic leaking. It is man made and has smaller molecules than dino oil. That is why it lubricates better. The down side is that same quality makes it find places to get out that dino oil can't. It is really that simple. It does eat gaskets or super clean things. It does not leave any depoisits that I could find when I pulled the rocker covers off at 97,000 miles on the 97.

PJ

Chrome383Z

I have to disagree with this statement. Given the same circumstances, same oil changes, a synthetic oil will allow the engine to operate longer (generally speaking) then with the mineral oil.

There are several things that a synthetic does better then a mineral oil. The BN is higher in the synthetics meaning that it does not turn acidic near as fast as conventional oil. When the oil turns to acid, your engine wears.

The synthetics have a much higher detergent property which will keep the engine cleaner. This property is based on the oils ability to keep the dirt in suspension longer so that the filter can take it out. Mineral oil is not as efficent so your engine wears.

The VI propertys of synthetic oils are Excellent. They have a high viscosity index which is good. The viscosity of the oils do not change as durastically as mineral oils do. Mineral oils have to have a VI additive added in to help them out and as this depletes, your engine wears.

Also, there are cost and environmental savings. 15,000mi oil changes are not unheard of with Synthetic oils (few exceptions). There is no way you will ever get a mineral oil to get close without immenent failure.


Now to the original question about using synthetic oils on your 80k plus engine. Using the synthetic oils would be great for you. BUT, you have been using for mineral oil for quite a while and it is not advisable to make a switch unless you monitor your engine very closely. Here is why: The mineral oil is not very good at holding dirt particles in suspension, there is also varnish from the oil oxidizing (low BN number). All of this dirt and sludge has collected in your engine for the last 80k miles. The synthetic oils (being a great detergent) will remove this when you first start it up which is a good and bad thing. It is good in you need to get rid of it. BUT, the bad part is that not only will this clog the filter; it has been shown to clog oil passageways leading to starvation in critical areas (cams especially). There are ways to do this right and I do not have any direct experience switching over so I cannot advise with actual experience. I believe there are products at your local Auto Parts store to facililitate this change. Might be worth a few hours on the Internet and some research to find a good recommendation on how to make the switch. Good Oil Analysis and Tribology website: www.noria.com

Greed4Speed

All good on paper, but in the real world an engine with conventional changed a 3k intervals will last as long. I know people with over 200k miles on work trucks (original drive train non-deisel) used in towing and hauling.

I have seen no one let their synth go for 15k miles, many still do the 3k change intervals. No environmental saving there since you're still supposed to change the filter. You do know oil is recycled right?

Very few people keep their cars past 100k, and even fewer performance car owners leave their engines alone that long. More lost benefits of synth.

mebanditws6

I make it a practice on any used car I buy to run a treatment or 2 of this: www.auto-rx.com, then switch over to whatever oil you want. A high mileage engine will benefit as much as a lower mileage engine provided the seals are good on both and both are clean on the inside with no sludge buildup.

Jason

Chrome383Z

I'm not saying conventional oil is bad, hell its been used for xxxxx years so its a decent lubricant. But to say sythetic is not better is like saying a ford pinto is a sports car...

Conventional oil is not up to the task of high mileage, or extended oil changes. Sure there are cars out there with 200k before they failed, my point is if they had synthetic it could have been 250k or 300k. Conventional oils wear the engines more in cold starts, high temperature, and when engines are old. When you start having blowby with worn rings it turns conventional oil more acidic whereas synthetic can withstand more...

I'm not saying its the cure all, but for todays engines it shouldn't even be a hard decision.

The vehicle I drive for work gets 10k oil changes w/ filter every 5k. 15k is definetely possible with vehicles w/ alot of highway miles. I drive in the city 50/50 so I back it down to 10k. Its an 01 venture and approaching 200k and is not leaking, or burning oil.

Conventional oil has served its purpose as did the carb, It's time to move on. It's not what has been achieved with conventional oil, it's what CAN be achieved with synthetic. Do some research on it. I've talked to Shell chemists (I work in Industrial Hydraulics) and they would run nothing but. It's a proven fact.

MarineReconZ28

Thanks PJ. I'll look into that.

Antz97ZNJ

why woudnt it be

rokudan

You must not know too many BMW owners...

I switched at 90k miles. No problems.

bunker

Sythetic all the way, take the engines apart and look at obvious things like pushrods after 200k on a sythetic engine and conventional oil engine, the sythetic one will most likely have clean shiny puhsrods while the conventional oil may have brown ones, especially if the engine didn't get up to temp or over heated at some point.

Conventional is ok for a work truck, a work truck does not hit 7k RPM on a stock engines on a daily basis, many LT1s stock high milage rev to 7k RPM daily, one of them being me and I would not dare use anything but true synthetic, and I prefer the Castrol Syntec German 0W30.