Dreaded RMS leak

[1999Porsche911]

Kevin, I checked the TSB and you're right. but 15-50 is noted in my owners manual. I live in a cooler climate area, but travel to high temp inland areas often. that's why I'm using the 15-50. seems the heavier 5w would be a harder cold weather start. I used Castrol 20-50 in my SC for years with no problem. would you recommend a different oil at the next change? Cheers, jl

Okay - one thing to get straight - the winter spec (0w-40) refers to viscosity when cold (there's more to it, I know). The 0 weight is thinner than a 5 or 15 weight when starting the engine at, let's say, room temperature (although the spec is at 0 degrees celsius). This means that it also circulates more quickly and covers the valve train, etc. regardless of the temperature. Hence, a thinner oil can reduce cold-start wear moreso than with a thicker oil which takes more time to penetrate and circulate to and through the tight engine tolerances.

I used to think you'd be crazy to run "thinner oil" but after reading lot's of threads, books, and conducting what I'd call "independent research" - I'm sold on using the factory fill in these engines. 5W-40 doesn't give any better warm-weather or high-temp protection than 0w-40, and it offers less cold-start protection.

So 'splain it to me Lucy - why use thicker oil unless you're spending a day at the track, running hard from dawn until dusk and not letting the engine cool down appreciably??? Not inviting flames - but interested in any intelligent reasoning.

Thanks much. I had my numbers wrong. the lower first number is the thinner, duh. considering what you've mentioned, I'll likely go with the 5w-40 at next oil change just on general principles. question: why would Porsche list the 15w-50 in the 2003 owners manual? why not have that multi-vis oil still on the approved list? thanks, j

It costs the oil manufacturer alot of money to get their oil recertified for the approved list. You'll most likely see a shorter list of approved oils as certifications expire (usually around 3 years) and many of the manufacturers choose not go through the expense of validating their oil.

[Loren]

Prior to 0W-40 Mobil 1 the recommended oil by Porsche was 15W-50 Mobil 1. Most of the older Owners Manuals state that.

[Tool Pants]

Oil fight.

I would not put that Mobil Water in my lawn mower....

[KevinMac]

No one said that 0w-40 vs 5w-40 provides any better hot protection. I simply stated that in my climate I don't need the 0W ( winter) grade where I live. In fact he 100 deg c spec are the same for both 0w-40M1 and 5w-40 Cast. The only reason I use 5w-40 is, it meets the European specs which is ACEA: A3, B3, B4, MB 229.3, MB 229.1, BMW LL-98, and Porsche approved. It would be nice if there would be a universal spec for all manufacturers- standardize. As a side note, BMW LL indicates a long life oil. BMW along with Porsche etc, have very wide drain intervals.This is not advocating one should follow the long intervals, just a spec that informs me that there is still protection there for long intervals. I follow manufacturer recomendations. Personally my view is why do they go through the trouble of making the recommendations if they don't provide any benefit.

[eDoug]

Prior to 0W-40 Mobil 1 the recommended oil by Porsche was 15W-50 Mobil 1. Most of the older Owners Manuals state that.

Okay - I've read through as many posts as I can on oil, and seen enough oil fights!

No sense in trying to argue an issue that has too many experts and individual viewpoints. I'll continue using Mobile Water (since the only tangible data point I have is a failed engine within 3k miles after the oil was switched to M1 15W-50).

But I still maintain the following items:

• lower weight = better cold start protection (related to "w" 1st rating on multi-viscosity oil)
  
  
• higher weight = better race (high-heat, high-rpm) protection (related to 2nd rating in multi-viscosity oil)
  
  
• less of an absolute difference in min/max for multi-viscosity = less additives and less viscosity "breakdown" over time
  
  
• oil change intervals = anything less than 5-7k miles is a waste (after break-in)
  
  
• oil analysis = why not if you have the time, patience, and interest (but you need to collect multiple data points for it to be valid)
  
  

The rest is up to us as individuals to decide - as far as I'm concerned, there's some level of rolling the dice. I don't think anyone, including Porsche, has a definitive answer on what's "best."

[KevinMac]

Prior to 0W-40 Mobil 1 the recommended oil by Porsche was 15W-50 Mobil 1. Most of the older Owners Manuals state that.

Okay - I've read through as many posts as I can on oil, and seen enough oil fights!

No sense in trying to argue an issue that has too many experts and individual viewpoints. I'll continue using Mobile Water (since the only tangible data point I have is a failed engine within 3k miles after the oil was switched to M1 15W-50).

But I still maintain the following items:

• lower weight = better cold start protection (related to "w" 1st rating on multi-viscosity oil)
  
  
• higher weight = better race (high-heat, high-rpm) protection (related to 2nd rating in multi-viscosity oil)
  
  
• less of an absolute difference in min/max for multi-viscosity = less additives and less viscosity "breakdown" over time
  
  
• oil change intervals = anything less than 5-7k miles is a waste (after break-in)
  
  
• oil analysis = why not if you have the time, patience, and interest (but you need to collect multiple data points for it to be valid)
  
  

The rest is up to us as individuals to decide - as far as I'm concerned, there's some level of rolling the dice. I don't think anyone, including Porsche, has a definitive answer on what's "best."

Agree with most points except the statement on absolute difference. This statement is true with dino oil , but synthetics have an advantage. The branched-chain structure of synthetic oils naturally resist changes in viscosity with temperature. It's just the way they're made. Therefore, true synthetic oils often don't need any viscosity improvers at all! This is one reason synthetic oils last so much longer than non-synthetics.

[Tool Pants]

I was at a local independent shop today. The 1999 C2 with 140,000 miles was in for a clutch replacement. No, this was not the original clutch.

Marvin also resealed the engine. When he was done I drew happy face on the back of the engine case.