trifona

Trying to decide upon what weight synthetic to go with.<p>Living in Philly, there are some pretty wide temp swings for a motor oil to deal with. Add to that "enthusiastic" driving, long distance driving (occaisional romps to Pittsburgh (300 miles), and overall high milage use (25K per year), and ive got some real issues to contend with.<p>When i called my dealer to schedule my 5k service, he recommended 5w-30. After doing some research within the archives as well as online, im thinking that the recommended oil wouldnt cut it for the summer months (90+ easy) or for overall turbo longevity.<p>I was leaning towards Castrol Syntec 5W-50 for its "seemingly" perfect spread: quick lubrication for winter starts, as well as heavy weighting for summer / high speed protection. However, after reading an editorial of it on an SHO website, its heavy use of modifiers has scared me off (see excerpt below).<p>That leads to the good old Mobil 1. 5W-30 or 15W-50? <p>I like the 5W for its cold starting attributes, but fear the 30 weighting for the summer.<p>The 50 weight seems to be the most reassuring choice for the turbo though; yet might be too heavy for winter time. Also it does have some of the modifiers as well as having a viscosity spread >30. I assume this isnt too much of an issue since many on the org use this weighting.<p>The one other monkey wrench is/will be my new job. I will be taking a train into work come June and will also be doing a fair amount of travel. This will put the car in situations where it might sit until late in the evening after work (pity me) or even worse, having the car sit for upwards of a week at a time while i'm away on business. How should this set of facts affect the oil choice?<p><br>Thanks to all,<p>trifona<br>'99.5 1.8tqms<p><br>http://www.shotimes.com/SHO3synthoil.html<p>"What about Castrol Syntec 5W-50?<p> From Gary Morrell: <p> 5W-50 is an awfully wide viscosity spread, even for a synthetic.<br> Castrol must be using a large amount of viscosity modifiers to<br> get this spread. Viscosity modifiers (VM`s) are long chain<br> polymers that are added to a light base oil to prevent it from<br> thinning excessively as it warms up. At cold temperatures the<br> polymers are coiled up and allow the oil to flow as the 'X'W<br> number indicates. As the oil warms up the polymers begin to<br> unwind into long chains that prevent the oil from thinning as<br> much as it normally would. Unfortunately, VM's will shear over<br> time, reducing their effectiveness, and can burn and form<br> deposits that cause ring sticking. Most manufacturers have shied<br> away from oils with more than a 30 point viscosity spread.<br> Notice how hard it is to find 10W-40 anymore? For awhile, GM<br> threatened to void warranties if 10W-40 was used.<p> AMSOIL uses no VM's in their 10W-30 and 15W-40 weights,<br> and Mobil 1 formulates their 5W-30 and 10W-30 without VM's.<br> Oils that start out with heavier base stocks, such as 15W-50 and<br> 20W-50 need very small amounts of VM's, however, I can't<br> recommend either of these 2 oils if your wintertime temperatures<br> go below 30 deg. F.<p> Try to keep the viscosity spread under 30 points, this will keep<br> your bearings happy."

trifona

BTW: Service Manager felt Synthetic was Overkill for the engine

Mike O.

I drive over 45,000 miles per year. I will use nothing but Mobil 1 15/50. I don't worry too much about the low viscosity in the cold temps. I use it in Connecticut all year long and the engine is still as tight as new. I did a compression test at 50,000 and every cylinder held pressure to "as new" specs. I do, however, make sure I have at least 160 degrees of oil temperature before I drive the car. That does mean sitting in a cold parking lot for several minutes at high idle (1500rpm) in the middle of the winter. <p>Hope it helps,<br>Mike O.<br>98.5 1.8TQMS, Wett 1.0, Stebro cat-back, Mintex, etc, etc, etc

Vlad N

Look at the redline website www.redlinoil.com. There is a nice technical write-up on synthetic oil properties.<p>I am personally a firm beleiver in advantages of synthetics specifically in turbo engines. After all synthetics were designed for jets, for the very same conditions turbocharger bushings runs at (50k+ rpm, high temps).<p>I also think that low viscosity synthetic (5W30) may actually improve engine power at the top of engine rpm range, because that is where turbocharger spins at it's highest rpm trying to maintain the boost level (especially for the tiny K03).<p>Vlad N.

DaveG

I will be getting an S4 in the fall. What weight oil should I run?<br>I drive my cars pretty hard, but may not have to rev it to hard in the 2.7bt<br>in order to get a good amount of tourqe. I also want to run<br>synthetic oil from day 1. I run Mobil1 in my current car. The only thing<br>that is still in tip-top shape is my engine -- tranny, suspension, etc etc is<br>shot. In the 2.7bt, sould I run 5w-30, 10w-30 or 15w-50? I live in NJ,<br>where the ambient temprature is varied through out the year (10 - 100<br>degrees F).<p>Thanks,<p>DaveG

Andrew C.

If you're going high mileage/year (and therefore several oil changes), you might consider a different weight for Winter (5w30) vs Summer (15w50) eom