Hello, Sorry fellers it has been a long time since my last post. I have a general question (please no negative comments). I have a 1991 Chevrolet Camaro RS that I purchased of some one and it has a TBI 350 out of an Impala or Caprice. I don't know the exact milage but it says 155,000 kilometers bt I don't know if that is just for the 350 or if that was also for the 305 or maybe the 350 has a sit load more. I am not sure about the history of this vehicle. Anyway I am going to do an oil change and I was getting oil from a local automotive shop by my house and one of the guys that worked there suggested I do an engine flush. This was a fairly younger guy who was into rice and all that stuff (although he was friendly). What do you guys think should I do an engine flush? I also bought 10w-60 motor oil. Is that okay I live in the Middle East were it gets really ****ing hot. Positive feedback would be very helpful thanks guys I appreciate it.

 

Engine flush? is a valid thing for some engines, but is also quick and easy profit for a shop. Shops treat guys who don't know what's up the same way they treat women. They push whatever they think you'll pay for. So, are you having issues with the engine? Our summers get up to 105*F, and when it's that hot, in higher-mileage engines, I move from winter 10w, usually 10W30 or 10W40, to 20W, for us it's 20W50. The first number, before the W, should reflect your engine's internal clearances, particularly the rod and main bearings. If those are where they should be, then a 10W should be fine year-around. But if the bearings are worn out, a 20W will help extend the life of the engine. What's an easy way to tell? Connect an accurate, aftermarket oil pressure gauge. Start the engine, and see how far off your factory gauge, above right of the speedometer, is. Then at idle, your pressure needs to be above 10 psi hot. If not, replace your 10W with 20W and try again. As for the number after the W, That'll affect your oil pressure after sustained high-rpm operation. If your engine is all stock internally, it won't tolerate much past 70 psi. Probably part of why the factory gauge stops at 60.

 

The number before the "W" is the cold temperature viscosity rating. It doesn't have anything to do with bearing clearances. The last number is the hot temperature viscosity rating. The two numbers use different scales, and really don't have anything to do with each other.

The problem with using an oil with a wide spread like that is they have to put in a lot of an additive called "viscosity index improver". VI improver basically expands when hot to make the oil act thicker. The problem with a lot of VI improver in each quart of oil is that is one of the first things to break down under heat in an oil, and when it breaks down, it no longer functions as a viscosity index improver, and isn't a lubricant. Basically, the worst of both worlds.

You'd be better off with a quality synthetic oil, or a straight-weight (no "W" number) oil. And, no higher than 40 weight.

 

Yeah, you're correct, except that the correlation I made is valid, and this OP seems to be what's called a "layman", and seems more interested in learning the whats and whys about his engine than learning about oil, so I presented just enough to answer the question, and no more, to avoid getting sidetracked. Lemme remind you, I'm a professional automotive machinist, 9 years now. I have a solid grasp of the correlation between bearing clearances and oil thick- or thin-ness. For example, you don't run a straight 40W in an engine with a max bearing clearance of 0.0020" in cold weather. The OP lives in a hotter climate, so I answered for that. Bottom line, the oil has the rating for a reason. Learn to take maximum advantage in the easiest way. By finding the correlation.

 

Thanks guys, after reading other sites I think I will skip the engine flush. I think I am going to use the 10W60 I have unless some of you think otherwise.