First, in using multi-viscosity oils, one must remember that the first number is for sub-freezing weather and important only during starting and the first few minutes of running, as the oil's viscosity is more a function of the temperature then. It is hoped that the oil reverts to it's higher weight as the engine temperature approaches 'normal'. The very modifiers that cause this actually break down the oil more rapidly as it becomes acidic, ie, after lots of short trip stop and go driving where moisture and metal wear components add to the mix. It was for this reason I chose a fixed viscosity 30W 'fleet service' oil for my first turbo, an '84 Dodge 600ES 2.2L. The highest service rating at the time was CD/SF, and that was with Pennzoil 30W 'fleet' oil, used by taxi's, etc, which I had to order by the case from a jobber. I later bought an '88 Sundance 5sp 2.2L, '89 Voyager 2.5L, and '90 Shadow ES 5sp 2.5L. All were turbo's... none had less than 130k miles on them when traded or sold. The Shadow probably had ~175k, hard to tell, as the odometer didn't work for it's last 7+ years. I changed the oil every 3k miles - or six months on the aged Shadow. All had 30W Pennzoil and Fram filters... and no engine problems.

About cooling... an engine is designed to operate in a certain temperature range. To keep that range relatively constant, it's cooling capacity exceeds any known needs - even with the A/C going in 100 degree weather. It is modulated, of course, by the thermostat and radiator fan. It can be taxed by contaminated coolant and/or poor heat flow in the engine or radiator due to contamination there - or even too many bugs in the radiator's fins. No doubt an engine will take longer to 'cool' in hot weather - and the oil's temperature can peak higher then as well, if it is not permitted to 'cool' before shutdown. Run at high speeds constantly - and with frequent turbo use - ie, racing - will tax the stock cooling system, of course. The one common replacement item in all of my MOPAR turbo cars - and my '93 3.9L V6 Dakota - was a new brass/copper radiator between 100-110k miles, the plastic tank/Al fin OEM units having developed leaks.

My wife's new '05 SRT-4 has had two dealer sourced dino oil changes... with their oil. I may go back to doing my own oil changes again. I will contact MOPAR re the use of straight 30W oil. I assume that the current turbo's have water jackets - a la the AiResearch original units. The best longtime insurance plan with them was to let the engine idle for 30+ seconds or so after a 'run' before shutting it off - preventing 'coking' of the hot oil in the turbo... and changing it on time. I know the attributes of synthetic oils at higher temperatures. Even the Jeep Liberty crowd likes it - but my '05 Liberty has also had only dino oil. If I raced - or had an air cooled engine - it would be different. Someone show me where I am wrong... if you can. Thanks!

Stainz05

PS Does the SRT-4 have an oil cooler? If not, why not add one? MOPAR Performance had a simple heater-line unit to be mounted between the filter/block for the 2.2L/2.5L... what is available for the SRT-4?

 

yes srt-4s have oil coolers.

 

yup

 

After "spirited" or "hard" driving the manual recommends a 3 minute idle to cool down the engine in order not to damage the turbo, or a bit of easy driving before shutting off the vehicle. Unlike other cars where as you stated it may just be 30 seconds. Little SRT likes 3 minutes to make him happy.

Im using 5w40 for my next change, currently 5w30. Just because it is whats recommended. However in the beautious cold of Rhode Island's winters my baby loved 0w-20, started RIGHT up regardless of temp, be it 0F or below. I've looked at the 30 weight oils and wondered about using them, but figured if the manufacturer (though they dont always know best as we all very well know) recommends a 5w30 (re-fabbed since the intial construction of the SRT-4 when it was only 10w30) then I may as well use it, and my car has no complaints about it, so I'm happy and so is he.