[Cloud9...68]

I know this topic has been gone over to death, but about a year ago, iirc, a few intrepid people, including sasilverbullet (in toasty central Texas, no less), went with a lighter weight oil than had been generally recommended previously. The ensuing discussion seemed to support that use of a weight lighter than the conventionally-accepted 15W50. I believe the concensus was that 5W40 in a modern synthetic like Amsoil or Redline is a good choice. It's about time to change my oil, and I would prefer to go with something like 5W40 due to the viscosity reduction resulting in potentially less internal resistance to rotation, and therefore maybe a smidge more power. Now that a few people have taken the lighter-oil plunge, have there been any regrets? Thanks.

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[sasilverbullet]

No regrets! I use Amsoil's European Formula which is pure synthetic 10w-40.



Since changing to this oil I've not had to add ANY oil in between oil changes.



My oil changes went from 5,000 mi using Mobil 1 15w-50 to 7,000 miles with the Amsoil. The oil even at 7,000 is cleaner looking and smells less like gas than the Mobil 1 did at 5,000.



I'm happy! <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[ds968]

I've been using Amsoil 5/40 Euro formula but only started about 6k miles ago ( previously ran on Mobil 15/50 ) so not sure how relevant the info is but...I do not detect much of a difference in how the car starts or how it runs, but the color on the dipstick definitely stays "cleaner" longer than the Mobil used to, and there are no problems so far. I'll continue to use it, since public opinion seems to favor the benefits of the ligher weight oils for our cars, particularly in a Northern California climate where temps stay in a fairly moderate range all year and extreme changes ( cold or hot ) are almost unheard of..

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[flash]

5 is a bit light for me, but i am very happy with the switch to redline 10/40 - much different than the mobil 1 10/40, and definitely better performing than the mobil 1 15/50

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[Cloud9...68]

Yeah, I was thinking of going with the 10W40, given the realtively warm climate here in central Texas.

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[Cloud9...68]

I just checked Amsoil's web site, and they only show the Eurpoean Formula in 5W40. I would prefer to go with 10W40 in the warm climate I live in, though I'm not sure how much of an impact the number to the left of the "W" would really have, since the oil only acts like it has the lower viscosity indicated by the number to the left of the "W" when the engine is cold. They sell a "high performance" oil that comes in a 10W40 weight. I'm not sure any of this makes much of a difference, but I'm curious, sasilverbullet, where you the found European Formula in 10W40. Thanks,

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[94SilverCab]

Just had my car at RS Barn. Pete is now reccomending Redline 15w-50 in my car. Was running 20w-50 until then. Maybe because my balance shaft seals aren't leaking any more?



Regards,



Jay

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[Cloud9...68]

Interesting... So Pete is still recommending relatively heavy stuff. Hmmm, that throws a new wrinkle into the discussion...

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[94SilverCab]

I did not mean to imply that you should put in your car what I have in mine, especially since our driving conditions are so very different.



By all means, do your homework, seek out specialists and if anyone ever comes up with a definative place to find just the perfect answer, please share!



There is a site http://www.bobistheoilguy.com/index.html I found it didn't answer my specific questions and I'm more confused than ever.



Jay



Here are my specs;



Live in Philadelphia

Drive 3,000 miles/year (2,000 in 65 - 95 degree heat, 1,000 on 32 -60 degree temps)

Oil is changed yearly regardless of # of miles (meaning I would never exceed 3,000 miles)

71,500 miles on car, well maintained, no leaks

Driving is always spirited, divided between highway/stop and go.

Frequent runs up to 6,500 RPMs <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[doster]

[quote name='flash' post='50506' date='Apr 7 2008, 05:55 AM']5 is a bit light for me, but i am very happy with the switch to redline 10/40 - much different than the mobil 1 10/40, and definitely better performing than the mobil 1 15/50[/quote]





+1 on the redline 10/40

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[flash]

dave greimann, who is the resident oil guru (castrol guy), wrote a pretty thorough article on the subject - he went through all the plusses and minuses of the different weights and formulas



i changed from the 15/50 mobil 1 to the 10/40 redline and got faster spinning and lower oil temps - if i were regularly running at over 270 oil temp heat, the 50 might be better, but i do not have that problem, so the 10-40 is more than up to the job

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[Cloud9...68]

The oil viscosity chart on page 63 of the owners manual sheds some light, but also adds some confusion. It seems to indicate the number to the left of the "W" has a greater bearing on the maximum ambient temperature in which the car is operated than the one to the right, which doesn't make sense to me. I would think the number to the left would only be important when first starting the car cold, and the one to the right would represent the maximum viscosity the oil will achieve, which would be important when the engine is at its maximum temperature. The chart implies that at 100F and above, 20W40, 20W50, and 15W40 are all acceptable choices, while 10W40 is only good up to about 90F, and 10W30 only up to 70F. So for you folks in California and New Mexico, 10W40 is perfectly fine, but those of us in places like Texas and Arizona, according to the manual, should stick with the heavier stuff, at least in the summer months. But of course, the chart in the manual applies to conventional oils, since synthetics weren't in wide use in 1992.



I just checked Amsoil's and Redline's web sites, and neither makes 20W40 or 15W40. But, to add to the confusion, Redline seems to indicate the 15W50 should be used primarily in engines that see extreme heat conditions, such as racing engines. So, I'm now more confused than ever <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" />

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[Cloud9...68]

I'm afraid that article doesn't really shed light on the question of what weight oil to use. I suspect that the superior lubrication capability of synthetics would allow the use of a lighter weight oil than is shown in the chart in the owners manual, but I wish I had some data to back this up. And with the added factor that many of our engines have a lot of miles on them (mine's close to 101K), with the resultant larger clearances, concerns me even more. I'd like to switch to a lighter oil than the 15W50 I'm using now, because the decrease in viscosity (which is defined as the resistance of a liquid to flowing due to the friction of its molecules) should translate into a bit more power, and maybe even slightly cooler running, because less of the chemical energy stored in the fuel would have to be expended in overcoming the friction of the lubricant, allowing more to translate to useful work, and less to lost heat, but I'm just not sure if it's completely safe in the hot climate my car operates in.

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[Cloud9...68]

Well, after doing a bit more research (Redline's web site is pretty informative), I decided it was safe to try a lighter oil than the 15W50 I had been running, so I went with Redline 10W40. Redline's site states that 15W50 is really only suited to engines that endure extreme conditions on a continuous basis, which really doesn't meet the description of most of our cars.





I can't say I notice any difference in things like smoothness of idle, operating temperature, or anything about the way the car runs, but it's definitely easier to crank when I first start the car. I thought my battery was getting weak (which it may in fact be), but now, it cranks like it's a new battery. I find this pretty amazing, considering the new oil is only 5 "viscosity units" lighter under cold operation than the old stuff. This makes me think the resistance to turning of the mechanical parts caused by the viscosity of the oil is significant, so it stands to reason that it may be making a bit more power when warmed up. However, this probably amounts to such a small difference that it's hard to notice, while the impact on cranking is much more easy to detect. So, overall, I think I made the right decision, and would encourage others to consider a lighter oil when it's time for a change.

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[flash]

i knew you'd like it

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[FRporscheman]

A smidge more power is worth absolutely nothing next to the healthy operation of the engine. Oil is the heart and soul of an engine. Just use the brand, viscosity, and formula that will ensure consistent sufficient lubrication.



I know this is cynical, but hunting for 1hp could rob you of 236hp.

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[gryphon]

I so agree, FR. Over the years manufacturers have chosen to redesign engines, and their lubrication systems, to use lighter weight oils, primarily to achieve slightly better fuel economy. If Porsche specifies a certain viscosity oil for a certain climate and driving conditions, I see no reason to deviate, only to chase an elusive HP or two. I live in Arizona and use Mobile One 15/50 year-round.



Tom

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[Cloud9...68]

I agree that one should follow the recommendations of the manufacturer, but there's a point to consider here - the recomendation in the owner's manual was based on the non-synthetic oils that were available when these cars were built. I'm not an expert in lubrication, but Redline's web site does a good job of explaining how the long chain molecules in conventional oils tend to break down at temperature, resulting in a decreased viscosity relative to a comparable weight synthetic. In other words, in terms of lubricating properties, a 10W40 synthetic behaves like 15 or 20W50 conventional. Also, the fact that my engine had so much more difficulty turning over using 15W50 than it does with 10W40 of the same brand, even here in warm central Texas, tells me 15W50 is just too heavy. Based on all of the above, I feel 10W40 is a better choice for my engine than 15W50, and certainly poses no risk whatsoever to its longevity.

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[gryphon]

Well said, Cloud9.



Tom

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[Cloud9...68]

Thanks. There's another point that I forgot to mention. Discussions about oil types and viscosity (along with topics like politics, religion, and sports teams) tend to get a little emotional and anecdote-based, because there's so little data available to back up the various opinions. Well, I forgot to mention that I took a sample of oil from my recent oil change, and I'm going to send it off to Blackstone labs for analysis. This oil was just about 4500 miles worth of Redline 15W50, that was in my engine for about a year. When I do my next oil change, I'll get another analysis, this time with Redline 10W40. I'll make sure I dod the change at exactly the same mileage as my last change to make the samples as comparable as possible. This way we'll be able to objectively compare the degree of wear in my engine with the two different weights of the same brand of oil. Sorry the results will be so far in the future, though. So, if anybody else, preferably the owner of a daily driver, has an oil change coming up soon, and are contemplating switching to a different weight of oil, would you mind getting analyses done of samples from the two different weights, to augment my data? It would really benefit the community. Thanks.

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