[Airport Towing]

I think you're right on about the 20w50 oil having a hard time flowing when cool, which would cause oil starvation when first started. I've seen it first hand here allot (I live in NY, and it DOES get cold here) Ditto on the drain back issues, especially if/when it hits the rotating crank, lots of oil above, but little below until things warm up. I've also seen pushrod, rocker, and valve train damage from thicker oils. I think if you need 20w50 to maintain oil pressure it's time for a rebuild, or the clearances are loose to start with. Of course, if your engine builder recommends 20w50, than you should use it, because he is the one who built the engine, so he probnably knows what he's talking aboout. The best answer to this may be to ask your Engine Builder what he/she reccomends and uses themself. Personally I use 10w30 Valvoline to break in new engines, and the first time out or first 300 miles (depending on engine application). After break in, I use Mobil 1 in all the engines and cars I build/own. I tear down and rebuild at least a dozen race engines every winter and can tell which guys are using the synthetic and which ones are not from wear and buildup. The difference is amazing. I can't see using an oil with a low number lower than 10, unless it's in a 4 banger, but lots of racers I know like the Castrol Syntec and run it all year. I do know that after your engine is broken in, synthetic oils are better against wear, heat and breakdown than regular motor oils (I fail to see how anyone could argue with this). I would say that your reasoning is sound and makes sense. I can't think of any drawbacks to switching to a synthetic oil other than cost. 2 more cents. :-)

[ November 26, 2002: Message edited by: Airport Towing ]</p>

[jobu]

Airport Towing - do you use Mobile 1 15w-50, 10w-30 or some other grade? I went to the Mobile 1 web page and copied some of their technical stuff for the 15w-50 and it sounds like its a good fit for my 400 engine. (see below) I live in San Diego so I think you're right about not needing to go below 10 on the low number of the multi-grade. Do you think the 15w-50 is too high a viscosity oil even though it's a synthetic? (I also included the Castrol Syntec sales pitch for 5w-50.)
____________________________________________
Mobil 1 with SuperSynTM 15W-50
+ Flows at -45°C (-49°F), pumps at temperatures as low as many conventional SAE 5W-30 oils.
+ Provides superior high-temperature protection for high-performance and high-revving cars.
+ Contains additional wear protection required for racing type engines.

Mobil 1 with SuperSyn� 15W-50 is a performance-driving formula that provides superior high-temperature protection for high-performance cars. It keeps protecting your engine, guarding against wear, even during hard driving.

Benefits of Mobil 1 with SuperSyn� 15W-50:

* Excellent for supercharged and turbocharged engines, muscle cars and amateur racers.
* The highest viscosity Mobil 1 available.
* Race proven.
* Superior high-temperature protection for high-performance and high-revving cars. Contains extra SuperSyn� anti-wear system.
* Mobil 1 with SuperSyn� 15W-50 is factory fill in Ford Mustang Cobra R.
* Exceeds API SL/CF.
* Exceeds ACEA A3/B3/B4-02.

Applications:
Mobil 1 with SuperSyn� 15W-50 is perfect for hot-running or heavily loaded vehicles and high-tech imported cars. It offers an extra level of protection, even under extreme use.
__________________________________________________
Here's what the Castrol Syntec web page says:

* SYNTEC Full Synthetic SAE 5W-50 provides the widest range of protection available. The 5W provides rapid oil circulation at start-up and the 50 delivers a thicker high temperature oil film for ultimate wear protection.

SAE 5W-50: provides the widest range of protection available. SAE 5W-50 delivers exceptional cold temperature pumpability for rapid oil circulation at start-up and provides a thick oil film for ultimate wear protection. Exceeds all car and light truck manufacturer's warranty requirements for the protection of gasoline, diesel and turbocharged engines where API SL, SJ, SH, CF or CD is recommended. Exceeds European ACEA: A3, ACEA B3, meets Japanese valve train wear and the engine protection requirements of ILSAC GF-3 for API Certified Gasoline Engine Oils, as well as Porsche, Volvo, BMW and Mercedes Benz.

[ November 26, 2002: Message edited by: jobu ]</p>

[Airport Towing]

I use 10w30 Mobil One in everything I have. I've run the 15w50 in the summer in race cars, but only when it's really hot outside. All around, Mobil 1 is a really good product. No, I don't think 15w50 is too high for your Poncho, especially in California (wish I was there, it's snowing here). Just make sure you check with your Engine Builder to make sure he is OK with it, just to make sure he doesn't have problems with using Mobil 1. :-)