20w-50

I ran 20w50 in my motor from 100k(when I bought the car) to 148k when I switched the motor, by choice. The motor is still in great shape it is just sitting on my garage floor. I did not really have a reason for running 20w50. It is just what I run in most everything I have so I usually have a few cases of in around. I run 5w30 synthetic in the new motor though.

the first number 10W, 15W, 20W is how it flows cold, you really want it to be thin for the cold starts. The second number, 30,40,50 is the actual warm flow rate. 5W30 and 10W30 will flow the same when the engine temp is at operating temprature, but the 5W30 will get to the parts quicker than the 10W30 on a cold start. That is why I use 5W30 Mobile 1. I have 143K on the engine now.

You might want to try 10W40, but why do you think you need heaver oil? Are you having oil consumtion problems. The 302/5.0 is a good engine, most last well over 200K with good maintence. Usually the valve seals are the first to go, which arn't a big deal, they can be changed on the car.

I wouldn't run the heavier oil in the winter - tough on the starter and the engine during cold starts. A 10W or 5W ought to get you through MD winters much better.

Mustang Rick, i also use 20W-50 in the summer. but that is in arizona with highs around 110*. i feel better about having some more viscosity once fully hot (need to do an oil cooler. Mr Yount's previous testimonials about his convinced me). and when it only gets down to a low of 80* if im lucky, no probs with the thick stuff.

i do run 10-40 in the winter, though i know a handful of guys from the dealer (service manager, for instance) that run 20-50 year around. all their mills have some miles on them, as mine does. i figure a motor with 150K plus on it has looser tolerances and clearances than when new. hence thicker oil being fine. for what its worth, i get pressure just as quickly with 20W-50 as 10W-40. if your temps are gonna dip down much (here, 40* is considered a blizzard), i would go with 10-40. i run it when lows get to around 60* or below, and highs are ~80* max.

i was just reading some stuff about how larger gaps in cold and hot viscosity (for dino oils only), cause less stability. the molecules get sheared easier, etc. the idea being that sticking with a smaller range is better for the longevity of the oil (less breakdown). does not apply to synthetics though; they are good to go. i want some 10W-60 (think that's Lamborghini's fill of choice). good cold and warm viscosity; little pricey though.

edit: you get cold dont you (i wasnt paying attention and assumed you must be somewhere warm since you asked)? if i ever saw freezing temps, i would likely use 5W-30 (per Mr Yount's suggestion). and i would use a good synthetic for some extra start up protection. i would not use 20-50 in any temps below ~50* for sure. your engine would rather pump vegetable oil than molasses. just my thinking. good luck.

Thick oil + cold weather = broken oil pump shaft !!!

The new M3 from bmw uses the 10W-60 as well.

im running 15-50 mobil synthetic on my 118k motor, that was for summer, ill prolly change for winter, is that what u guys suggest? or is 15 ok for NY winters?...whats your views on going back to REG oil from synthetic, is that "u cant/shouldnt do it" thing a myth?

Mr Yount, that was my foggy recollection (from one of your posts), but i wasnt sure and didnt want to give bad info. what is it for? the Z8? i think you had said it nice and pricey. i know the Lambo's is, and if not used, it voids the factory warranty.

Brodeur, i would go to something lower viscosity if it gets as cold in NY as i think it does. the cool thing with synthetics is that i trust them to lubricate better with less viscosity (and really help in cold start up, IMHO). for instance, i know of folks using mobil 1, 0W-30 in cars that get driven!!!!!!!! thats one thing for a 10 second blast down a track, but another entirely for driving around in traffic. (im certainly not saying to duplicate their actions. just an example).

i would go with 10-40 or maybe even 10-30, depending on how warm it gets there (im out of touch; i havent seen anything colder than 40* in years. LOL). and i would stick with the synthetic for winter. few bucks is nothing. peace of mind is worth it, IMHO. you should be able to switch back to regular dino oil (more and more "synthetics" are cracked- the base is dino oil, not synthetic). this makes the transition easier. some people have no problems, some see some leaks and burning. going to dino from a synthetic is s'posed to be easier.

id just go with the 10-30 or 40 and call it good.

New M3

Hey HISSIN 50 I was under the impression from what I read on the Mobile 1 site that the synthetic 15W-50 would flow just as well in cold temps as a dino 10W-30? Maybe wrong though I need to research it more.

Research it more - the 10W or 15W rating describes the oil's cold temp characteristics regardless of whether it's synthetic or dino. Now, take both dino and synth in the 10W rating, and take them to even lower temps than the rating occurs at, and you'll see the cold flow benefits of the synthetic. But, for any oil that has the 10W rating, it meets the flow characteristic requirements at the lower temp of the rating scale. Read at the link below for more data - I copied a piece below. Look at the pour point temp. differences within a given rated oil and you'll see the differences I was referring to. http://www.vtr.org/maintain/oil-overview.html

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if it is used. It was not included in this article for that reason. 20W-50 is the same 30 point spread, but because it starts with a heavier base it requires less viscosity index improvers (polymers) to do the job. AMSOIL can formulate their 10W-30 and 15W-40 with no viscosity index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no viscosity improvers in their 5W-30, and I assume the new 10W-30. Follow your manufacturer's recommendations as to which weights are appropriate for your vehicle.

Viscosity Index is an empirical number indicating the rate of change in viscosity of an oil within a given temperature range. Higher numbers indicate a low change, lower numbers indicate a relatively large change. The higher the number the better. This is one major property of an oil that keeps your bearings happy. These numbers can only be compared within a viscosity range. It is not an indication of how well the oil resists thermal breakdown.

Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons. The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 F is the minimum to prevent possible high consumption. Flash point is in degrees F.

The Shape, that is the impression from what i have read as well. many are of the mind that M1 15-50 is actually a "thin" 15 weight, being more closely related to a 10 weight. i was just readin about this last night, and the worries were that this meant that there was a possibly greater viscosity differential, which causes problems that Michael talks about (i did not have a chance to really read that whole post - i gotta finish something).

it seems that M1 uses the synthetic properties to keep the oil lubricating like a 15 weight when warm, even though it is 'thinner' than a 15 weight dino oil (group II would be). this allows the M1 to flow much more like a lower viscosity weight when cold.

all of this changes depending upon which type of oil is being talked about. M1 is PAO, whereas many other "synthetics" are a group III. many blends are group II and III mixed (constituting 10-25% use of synthetics, although this includes group III's). it is too bad that there is not more clearification of definitions on what a true synthetic is and regulation of those definitions. but they do react and perform differently from one another.

i have more thoughts, but i gotta run. ill check in later to see what people have said.

I was kinda wondering about that as well I know as Michael has stated that the greater viscosity differential in say a conventional 10w-40 is a bad thing, but I was thinking that didn't matter with the mobil1 15W-50 since it was synthetic? I just switched to the 15W-50 less than two weeks ago and it does make a dramatic difference in the stability of the oil pressure from what I was seeing with dino 10W-30. As we have talked about before I was only getting like 20-25 psi at hot idle with the dino oil under normal driving conditions. However under the same conditions the lowest pressure at idle I see with the synthetic 15W-50 is around 37 psi. Even if I beat the crap out of the car with the A/C on I still have atleast 30 psi at hot idle. I have noticed as many others have that a small oil leak I had from my low oil level sensor has already became worse since switching over. I feel though that having to fix a few oil leaks is a fair trade for the better protection and more stable oil pressure the 15w-50 synthetic is giving me.

Technically, Michael didn't state it -- the author of the article did; Michael just copied it. From my post above -- "Read at the link below for more data - I copied a piece below"

Michael, i got around to reading the article later last night; nice choice! good info.

The Shape, thanks for sharing your experience. i am playing with goin from Group II and III to M1 15-50. i was expecting to see a drop in pressure, and i still do. however, the extra flow capability when bone cold is a nice thing. also, knowing that even though my pressure has dropped, but the oil is clinging better, may make me feel ok about it.
TS, i dont know about you, but within reason, i could care less about leaks vs knowing i have better protection. i have always felt that way. i leak with dino oil anyways. LOL.

i just thought of a topic, and rather than tag along here, i am gonna post it. please answer if you feel like it.

Shape, im glad you are happy (and that i did not give you really bad advice). LOL.