Motor oil - What viscosity do you use?

[1jeep]

Don't take this any other way then me just being curious, but I would like to see how you timed that test. You can't just go buy an oil pressure gauge and see when it hits optimal pressure. You would need to run it through some kind of bench machine that has the same type of oil ports with a gauge on the end or something. Plus it would depend on the pump.

We had a lady bring in her Chevy dually for an oil change. Of course the hood tech sold her a transmission flush. The truck had over 100k miles on it and I bet it had never been serviced. This fluid was god awful. I warned him not to sell her on it because the fluid was probably the only thing keeping it running. Sure enough, once they flushed it (all they did was drop the pan and changed the filter) the truck didn’t leave the parking lot. The new fluid wasn’t thick enough for the old pump to pick upBecause we sold it and the truck was running when it came we had to buy her a new one. He lost his job.

My point is if the pump on the engine is worn it very well could be that it needs the heavier weight oil. And I would say do it with the same type of oil, synthetic or not.

[Lindel]

Perhaps not a scientific test, but valid none the less. Go buy your favorite brand of light, conventional motor oil, and a quart of the thickest synthetic you can get.

Put them in the freezer for the same amount of time, say a day or two and let them get COLD. Then take one in each hand and (after you take the lids off) upend them. See which one pours more willingly. Heck, make the conventional a 5W20 or even lighter if you can find it.

I think you'll be surprised at the results.

[Rich88]

20-50 synthetic to maintain oil pressure. And that's using a pump cover steel plate and oil cooler too.

Once fully hot, I'm 10lbs idle, 35lbs @ 65 according to Mr. Sun Pro.

[mark j]

0w-20 amsoil in the '09 rubicon- the manual calls for 5w-20. Ran the original factory oil to 2K miles then switched to the amsoil. Run amsoil filter with filtermag and change every 5k miles. In the '89 I have 2k miles on the built 401 with 15w-40 rotella with GM EOS now on its second oil change. I run Wix filters on this. I am going to make the switch to amsoil 20w-50 soon along with amsoil filters or K&N. Trouble is I changed the intake manifold gasket at 2k and I didn't see any polishing of the cam lobes at all - they still have that fine shot-peened look. So, I am not sure if I need to let it 'break in' a little more before going synthetic. I am running a 7 quart canton pan so I suspect the oil is not going to break down as fast which may contribute to the lack of visible break in. The '72 burns oil so fast it just gets 15w-40 rotella until I rebuild it.

[247pia]

We had a lady bring in her Chevy dually for an oil change. Of course the hood tech sold her a transmission flush. The truck had over 100k miles on it and I bet it had never been serviced. This fluid was god awful. I warned him not to sell her on it because the fluid was probably the only thing keeping it running. Sure enough, once they flushed it (all they did was drop the pan and changed the filter) the truck didn?t leave the parking lot. The new fluid wasn?t thick enough for the old pump to pick upBecause we sold it and the truck was running when it came we had to buy her a new one. He lost his job.

My point is if the pump on the engine is worn it very well could be that it needs the heavier weight oil. And I would say do it with the same type of oil, synthetic or not.

What happens is when the fluid is not changed in an automatic transmission the fluid doesn't do it's job any more of cooling and cleaning. The spools get worn and build up varnish in the worn spots.

When he put new ATF in it started cleaning and cleaned the varnish off of the spools which let the fluid by-pass causing a pressure drop and lack of movement.

If he was fired he wouldn't want to work for an irresponsible shop like that any way.

Owner should have been told: Your transmission fluid has exceeded it's service interval and has likely done damage that will eventually cause your transmission to fail. Your fluid needs changed but if we do that you need to sign "documentation" understanding that it may experience a pressure loss and failure of the transmission. We can change it for you now and take a chance at extending the life of the transmission or you need to plan for a rebuild as your transmission could fail on you "not unexpectedly". All people have to do is be honest with the customer and a lot can be prevented.

Then tell customer: My advice to you is not to change your fluid as it could go out tomorrow or three years from now (from my experience). But the signs of an eminent failure are there so I would start planning for down time and transportation arrangements to have your transmission rebuilt.

[letank]

What happens is when the fluid is not changed in an automatic transmission the fluid doesn't do it's job any more of cooling and cleaning. The spools get worn and build up varnish in the worn spots.

I have heard the varnish theory and wondering if it is this varnish or dirt and metal shavings? We have a good example above where the truck did not move after an oil change, but when you consider the amount of pressure and heat generated inside a trany, it seems like nothing can really hang on to the shiny pieces of rotating metal, the transmission line could probably be used for pressure washing.... or is it simply the servo clearance that has execeeded the service limit, could running a thicker oil help?

Inquiring mind here.

And yes I use rotella 15w40 for the last 2 years. The only time I use 10w30 in the warmer month one lifter failed, so I stayed w 10w40 castrol.

[FSJunkie]

Castrol Edge with Syntec power technology, or something like that. 5W50 and specifically blended for older style engines with the perfect amount of ZDDP (1400 PPM). It's good for all year round. Now, I know that the wider the viscosity gap, the more additives and less base stock oil. But I feel safe.

[heepin2906]

Pressure

it seems like everyone puts too much faith in the old pressure gauge. seeing as it is the easiest way to check for flow, it seems the likely gauge to have. but just because you have high pressure doesn't mean that you have a lot of flow. flow is in my mind the most important thing, just because your using heavy weight oil and getting higher pressure, remember it could be because you have a blockage and trying to push heavier oil through that small hole, why do you think high blood pressure is bad in humans? just a thought to keep in mind.

[FSJunkie]

low pressure+high flow = high pressure+low flow. It's just like electricity. Everyone puts in thick oil at the price of cold start wear. Most engine wear occurs at cold start and warm up, so I tend to lean towards thinner oil to help prevent wear at those critical times. 10W30, 10W40, or 5W50.

[joe]

I agree with most oil threads.
Yes, by all means use motor oil in the engine.

[Rich88]

...but just because you have high pressure doesn't mean that you have a lot of flow. flow is in my mind the most important thing, just because your using heavy weight oil and getting higher pressure, remember it could be because you have a blockage and trying to push heavier oil through that small hole, why do you think high blood pressure is bad in humans? just a thought to keep in mind.

The day the engine leaves the factory (or a properly done overhaul) the oil pressure is as max'd as it will be and will only decrease from there as bearings wear and passages open up.

There has to be some assumption, and that being there are no oil blockages. If one does have an oil blockage somewhere then no matter what viscosity you use that part is going to have premature bearing failure, and the conversation is moot.

The oil pressure, being a measure of back pressure is an overall indicator of the general wear on bearing surfaces as well as the oil pump itself. The more the bearings (or pump) are worn the greater the passage for oil flow and the less back pressure. If one observes that that oil pressure is lower than desirable its safe to assume that oil flow is not an issue, but the bearing wear factor is. In theory you cannot have too much oil flow, but in practice a lot less is required than one may think.

Because of the basic physics of the matter, increased bearing wear and resulting lowered pressure would necessarily result in increased oil flow.

However, on these old beasts, the oil pump design is infamous for wearing and becoming self-bypassing. This will result in a lower pressure reading. And you can now ask the question: Are the bearings worn and pump OK, or are bearings OK but the pump is worn? The latter is of special concern because now oil flow may in fact be compromised. In this case, a band-aid is to go to heavier viscosity to be on the safe side. Further, higher viscosity oil will increase the wear protection a bit more. This will extend the useful engine life. The only real problem is when someone thinks going to a higher viscosity actually cures anything in the long run and runs the engine to the point of failure and breakage at great inconvenience and expense (i.e. family camping vacation 300 miles from home) instead of doing a pre-emptive overhaul.

[scorge30]

My '83 Chero Pioneer came from the PO with a freshly rebuilt AMC 360 with roller lifters and an RV cam of some sort. When the new engine went back in the PO romped on the Chero (typical kid) and blew the tranny which might have had as much as 149,734 miles on it.

The rebuilt engine has less than 5k miles on it, and has a Edy 4 barrel intake and a Edy 4 barrel carb.

So I had to get the tranny rebuilt again (it was supposedly done last year but no proof) this time using HP parts, with kevlar bands, and a 4 pinon planetary and a Trans Go shift kit.

Not sure what oil the PO used but it looks like Great Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogleye and needs to be changed. Got a cheap Jiffy Lube filter on it now. Oil is black as night and smells bad.

I usually run 10-40 in my trucks, the RV gets 10-30 as that is what the manual calls for. The Chero has a Milodon pan on it and I am adding a dual remote filter mount and an oil cooler. I plan on using either Valvoline or Castrol 10-40 syn blend with one maybe two STP oil additive bottles.

I might toss a bottle of either Risoline (sp?) or a quart of tranny fluid and change the oil again in 500 miles to help clean the engine out. Not sure its state but the oil looks bad and I want to ensure it gets flushed out. I run a magnet around the filter which is supposed to cut down on wear.

Oil discussions are great as everyone has their own opinion, likes and dislikes. On our family farm my father and grandfather never used anything but Valvoline, Castrol and Rotella.

My wife's DD gets full syn 0w-20 as that is what the manu recommends and it is still under warranty. Lovin her 33 mpg though and oil change every 8,000 miles.

[FSJunkie]

I think that most of us would agree on what the perfect oil for our engines would be. Something that flows well at cold starts in the winter and is thick enough to maintain an oil wedge between parts in the hottest days of summer. Sounds like a 5W40 to me. We also want something that contains anough zinc and other high pressure anti wear additives to protect our camshafts and piston skirts. Something in the 1200PPM range is the best concentration for this. We also want an oil that protects against wear as much as possible, synthetic is good at that. I've heard all the tales of synthetic making leaks worse, not being compatable with dino oils, etc. I can tell you that when I switched my 123,000 mile motor over to syntho, it didn't leak any worse than it did, ran smoother, ran cooler, and if you mix dino and syntho together in a bowl and stir them up, they mix just fine. Synthetic is dino, it's just highly refined. It's not made of pig eyeballs or anything like that. With that out of the way, the perfect oil for me would be 5W40 classic car formulated synthetic. Castrol offers a 5W50 classic car formulated synthetic called "Edge with Syntec Power technology" It has more zinc in it than what it replaced, which had 1200 PPM! It is API SN, SN is designed to help counter the effects of Ethanol. Somehow Castrol found someway to have a 1200PPM+ SN. I encourage you guys to take a look at it. It's sold at Napa.

[jeepsr4ever]

You want high pressure in an AMC V8. You do not want low pressure and low pressure in a AMC V8 does not equal high flow. You also dont want to run the thinnest oil out there either. Viscosity is related to shear strength so if yu have thin oil the chances of metal on metal contact is greater than thicker oil. The thinner oil is shed faster as well. The large gears and pump body of a AMC V8 oil pump do not like thin oil either. As the oil warms up it thins out like crazy and this makes it harder to pump the correct volume to the bearings. If we had NASCAR oil pumps that were super accurate then thinner oil may be better however most are running pretty std street engine tolerances which wouldnt be as good.

90% of AMC V8s out there would benefit from a good oil filter, 10w30-10w40 in the winter and 15w40 in the summer. Depending on mileage of the motor.

If you really want to make a difference just change you oil regularily. These are classic motors now with the youngest at 20 years old you dont have to involve too much rocket science.

[robert cowan]

i run straight weight valvoline 40 weight in summer and 30 in winter since they took the zinc out of regular engine oil. valvoline race oil still has zinc. also when its real hot here i run 50 weight too.