MM120

it's been between 90 to 110 degrees here everyday, & was wondering if it would be okay to do this w/out any probs. I don't remember what the temp vs. oil wt chart says.

moribundman

I've been going to Bob's lately, and I've done a lot of reading on oil, viscosity, HT/HS, and all that stuff.

The oil chart in my '96 manual says to use the following full synthetic oils:

5W-30
5W-40
10W-30
10W-40
10W-40
(0W-40 oil should be okay, but is not listed in my '96 manual)

<b>Those full synthetic oils work for all temps.
Ideally you want to use oil that meets VW502.00.</b>

Mobil 1 0W-40 meets VW502.00. That's what I'm using at all temperatures (32-115 degr F ambient). Now, according to Bob's site, M1 0W-40 thins out to a 30 over time, then thickens back up, and I don't like the sound of that. There are two full synthetic oils I'm now considering. Both are supposed to be first-rate oils, but they are a couple dollars more per quart than M1.

- Lubro Moly 5W-40
- Pentosin 5W-40

Do you really need a thicker oil (talking about the second number in the designation? For example 10W-30 versus 20W-50):

- thin oil flows faster, moves heat away faster from critically hot parts
- thinner film means less friction ---&gt; less heat, better fuel economy

I suspect (tho' at Bob's they won't admit it) that a ticker oil can be of advantage when running an engine really hard (track, desert). I bet a 15W-50 wouldn't be out of the question under those conditions. I DO believe (I've got NO proof) that a thin oil might just crap out under EXTREME heat.


Dino oil is different. The ambient temperature is important with those oils:

For temps over 100 degr F, 15W-40, 15W-50, 20W-40, or 20W-50 are recommended. Odd also: the manual warns not to use 5W-30 at high ambient temps and/or for long distance highway driving.

One would think viscosity recommendation has little to do with if it's a synthetic oil or a dino oil. Not so. It seems a synthetic oil protects like a dino oil that is rated one viscosity higher. A XW-30 synthetic will protect as well, or better, than an XW-40 dino oil.

<b>But: DON'T DO IT! Stick with full synthetic oil</b><ul><li><a href="http://theoildrop.server101.com/cgi/ultimatebb.cgi">Here, you may want to take a look around...</a></li></ul>

Roger A. Ellis

<ul><li><a href="https://www.audiworld.com/search/index.html">https://www.audiworld.com/search/index.html</a</li></ul>

JWG

My mechanic initally turned me on to the idea, because he is a strong believer in using heavier weight oils in cruel summer heat . . . he sees lots of Bimmers and VW's looking especially worn from using 10w-30. It just does not protect most people that put on over 25,000 miles/year in stop-and-go traffic in 100+ degree conditions with the A/C running.

Thereafter, another mechanic I respect, Lloyd at TDL, said the same thing . . . a 12v in high temps should always run 20w-50.

As noted by others, you will lose a little gas mileage, but I would never drive my 12v to Las Vegas in 120 degree heat and at sustained 70+mph speeds up those long grinding passes without a 15w50 or 20w50.

Mobil 1 15w50 has become the de facto favorite of Porsche and BMW owners. I believe Amsoil makes the best oil in its Series 2000, but you have to pay more for their quality. Valvoine's new full synthetic also did exceptionally well in a recent oil analysis comparison of big name oils that I reviewed--even beating Mobil 1; however, I heard that their higher quality has correspondingly increased the cost of the product (in the auto mall where my mechanic has his shop, several of the small shops that used to carry Valvoline have switched to Castrol for their "ordinary" oils citing the price increase).

Like most things, its a balancing act between quality and price; market perception and reality; cost and profits. So, just put in a full synthetic 15w50 or 20w50 from a respected brand and be done with it. You will enjoy the protection during these scorching summer months and then you can switch when it cools down (after the October and early November Santa Ana wind season if you live in Southern California).

moribundman

What do you say to the claim that the thicker oil will cause the engine to actually run hotter and to cause more wear due to increased friction?

When I was talking to the oil gurus (The guys who have an oil analyisis done for breakfast :-P ), they all started yelling at me for even considering M1 15W-50. They predicted increased wear and a hotter running motor. The clearances issue came up, but until today I'm not sure if our 12v engines have maybe relatively large clearances, which may warrant a thicker oil. The Redline site recommends their 20W-50 (unless I remember incorrectly!) only for motors with large clearances. Do you know if our 12v engines have large clearances?

Also, when dealing with full synthetic oil, the manual does not recommend any oil heavier than 10W-40. They recommend 20W-50 only as a dino oil.

Now, the M1 15W-50 did look tempting to me (As I said I tend to pick rather a thicker oil than a thin one), but after all the negative feedback I got I was dissuaded.

VAP

I've been running Redline Racing 30wt in every car I own and for over a decade. I've had the heads off my S4 as well as the oil pan. I've had the pistons, rods out and the valves, springs, cam &amp; crank out of the engine and turbo disassembled and up on the workbench. At 97k this car appeared to be brand new inside. No varnish, sludge or other oily residue. Didn't even have that brownish hue that is so fond of aluminum surfaces inside an engine. All bearing surfaces were within minimal wear specs and rod bearings showed no scoring whatever. Perfect wear patterns on all lifters, cam lobes and valve stem caps and bodies. No measurable ridge at the top of the cylinder walls and 100% of cross-honing visible in 360 degrees of every cylinder. All rings were at their original factory gap and ring groove widths were the same as they day they went in the engine. All told the entire reciprocating assembly and bearing surfaces in the engine were still within 99% of their assembled "minimum" wear specs.

The only new car I've owned since the S4 is a 2000 TT and I got rid of it long before warranty was up but put Redline Racing 30wt in it at 5k miles. Only put 16k miles on the car total before selling it so I have no way of knowing the long-term benefit/detriment of that (but I think I know).

I use the same oil year-round and have never suffered anything remotely close or even similar to an oil-related failure. I prefer the straight weight oils due to purity without contaminating/modifying/lengthening their polymer strands yadda-yadda to achieve multi-viscosity ratings. I just let the car warm up a little longer before taking off in cold months. Hey I'm retired and not in any hurry even in the summer. And I always let my cars idle-down after a hard run.

But more than anything the straight 30wt just works for me and has for years and years. And I try to avert my eyes from any oil discussions and seldom will join in on one as I have here. Mostly because some of the things people talk about sound so f*ing wonderful and magic in print that I want to jump on every option the pro/con side are offering. Then I remember what works for me, how long it's been since I've endured an oil-related problem and ask myself; if it aint broke why are you so eager to fix it!?! That usually (but not always) snaps me back to "my" reality.

But I'm no authority on the subject. Far from it. Won't even make a recommendation as to what anyone should/shouldn't use in their cars. I just plod along doing oil &amp; filter changes every 5k miles and all is good in my little corner of the world.

And I do run redline in the tranny and the FD in my cars as well. But I use the lighter weight 70-80 MTL in my trannys as I like the way it makes the transmissions shift, especially in winter but in summer too. And again all my cars transmissions are fine after long-term use and occasional abuse... well, abusive as a day at the local road course permits.

moribundman

I know you use straight 30 weight oil, and sure, if it works for you that's great. Clean stuff without viscosity improvers. That oil shouldn't shear down at all.

Can you maybe tell me anything in regard to the clearances our engines have? Are they relatively small or large?

bogelo

I tried castrol 10w-40 synthetic, but they are not good. The heat climbs even more than the mobil1 10w-30.

JWG

I have seen so few available, especially at local shops and in full synthetics. I would love to get some more ideas from local mechanics, but I found no one who stocks and runs straight weight oils in my area. I hesitate to try something that no one else in my area has tried. On the one hand, I do not fix something that still works fine; on the other hand, I tend to be a native Californian--very progressive and experimental. Split personality disorder?

Going back to multi-weights, when I run 10w40 in the winter, it gets dirtier much more quickly than the 20w50 weight stuff I run the rest of the year--The heavier weights still remain translucent after 7500 miles; the 10w-40 consistently comes out more black and opaque. Rationally or not, based on this observation, I strongly endorse using the heavier oils especially during the hot summer driving I do. I just cannot reason that oil which came out dirtier protected better than oil which came out cleaner. If someone can debunk my logic, I would love to learn something new about oil protection.

Regarding engine tolerances, three mechanics to whom I spoke said that the tolerances do not mean much after 100,000 miles, because the engine has thoroughly broken itself in by then. However, they also agreed that on a newer engine they would run lighter oils solely to accomodate the tighter tolerances. Note: (Up to 90,000, the dealership I went to used 10w-40; thereafter, I started getting referrals and interviewing several local mechanics as I looked for someone more competent than the dealership that thoroughly screwed up my ignition by using the wrong spark plugs and idiotically trouble-shot the misfire problem. Having never turned a wrench on the engine, I, out of frustration, researched the issue and figured out the error before their "master technicians" to whom I ignorantly entrusted the car over half a dozen times after recognizing the misfire.)

It's amazing, 65,000 miles after getting totally frustrated with the dealership's incompetence and self-educating myself most every night on the internet, I have learned a heck of a lot about cars.

moribundman

"It's amazing, 65,000 miles after getting totally frustrated with the dealership's incompetence and self-educating myself most every night on the internet, I have learned a heck of a lot about cars."

I couldn't agree more on that!

Back to the oil: There are two schools of thought on the color of used oil:

1. Oil that comes out clean does its job, so it stays clean.
2. Oil that comes out clean doesn't do its job - all the dirt is deposited on the inside of the engine.

I used to use Castrol Syntec 5W-50 (I was ignorant about "fake" synthetics then). That oil stayed cleaner looking than any other oil I've ever used. I then switched to M1 0W-40, and that oil gets darker sooner.