I went to the local Lube It to get my oil changed. I had them fill it with Mobil 1 (which they charged me $7 per quart for. I learned my lesson!!!!). They told me that I need to stay with synthetic oil now and should not switch back and forth. Is this true or can I switch back to the cheaper "real" oil?

Buy it at Target - they have in NOCAL for 3.79 per quart.

You are OK to switch back and forth between synthetic and conventional "dino" oil. Mobil-1 is 100% compatible with conventional motor oils. However, I'd consider staying with Mobil-1 especially if you drive a 1.8T.<p>Andy Hedin<br>'97 A4 1.8Tqms, Wett 1.0 Bar Chip, ABT Filter, Mobil-1 for the past 25,000 miles....

go back to Dino, seals shrink, voila! oil leak.<p>True/False?

<b>Info pulled from the archives. Originally posted on 2/20/98 by Dave M:</b><p>"I have never heard any definitive discussions either supporting or debunking the myths surounding synthetic oil. I tried to read as much as I could regarding synthetic oils before I switched, and here are the conclusions I have come to.<p>1) MANY years ago, there may have been a problem with Mobil 1 regarding seals and gaskets. It had something to due with two substances in their formula that would swell and shrink the seals/gaskets at different rates. This is reported to have been corrected a long time ago.<p>2) It seems that the majority of the leaks attributed to synthetic oil were actually present before synthetic oil was even used. The leaks were just plugged up with sludge from the conventional oil and were most likely caused by the same gunk since the oil could not reach the seals/gaskets.<p>3) Adding conventional oil to synthetic will reduce the one property of synthetic oil that is important to me with my 1.8t - the high flash point (coking resistance).<p>Now I don't claim to be an oil expert or have all the correct answers on this topic, but I have tried to make an educated decision. There seems to be a lot of conflicting/mis-information floating around on this subject (just as there is for oil change intervals), but the majority I have seen seem to support my conclusions."<p><b>On 4/7/98 Dave M wrote:</b><p>"From what I have read, this USED to be a problem with synthetics, but has been long since taken care of. Mobil 1 is often cited in this regard, and they changed their formulation a long time ago to correct this problem. Seal formulations continue to be improved as well, but some older cars (15+ years maybe) might have seal problems with synthetic oil. I doubt Porsche and GM would be filling their cars at the factory with Mobil 1 if any of this were still true. <br>I believe most leaks are caused by switching to synthetic oil AFTER the seals have already been damaged. This is due to varnish and sludge buildup keeping the oil from reaching the seals. Changing to synthetic oil will tend to clean out these deposits, letting oil once again reach (and pass through) the damaged seals. <br>One of the reasons I am putting synthetic in my 1.8t is because of it's higher flash point. To me it does not make sense to add a small amount of conventional oil, since that small % of conventional oil could still coke up in the turbo."<br><b> Now, I don't know if "Dave M" is an expert on synthetic oil and seals, but it does sound like he's done his homework on the subject.<p>Andy Hedin<br>'97 A4 1.8Tqms, Wett 1.0 Bar Chip, ABT Filter...</b>

In a car as new as an A4 you have no worries. There have been extensive discussions on BMW re this subject. As there are plenty of old BMW's out there, they are indicative of what can happen. Generally, you are ok to switch to synthetic at any time if the car has had regular changes, i.e. no sludge or deposits on the seals. If the car wasn't maintained you may get leaks when the synthetic cleans up the engine. <p>kjk

Man, did I write that!!! :-)<p>No, I'm not an expert on these topics, but I did try to do a lot of research on them. Most of my research was web based, FWIW, but I did visit a lot of oil manufacturer sites, other car enthusiast sites, and also relied on information from the oil FAQ, people like Pat Gauss (of MotorWeek) and I think our own Erik B (who works in the oil/gas industry). I still believe that information to be true.<p>Dave M - 97 1.8tm, Mobil 1 for life

I asked my regular mechanic about Mobil 1, and was told that it should ideally cause no problems, but told me of 3 Audis that came in with problems after they switched. All 3 got sludged up. I'm very keen to try the oil, but with the climate here the way it is (hot and humid ALL year round) is the sludge problem likely?<p>AdrianC

Like most companies, Mobil makes their Mobil-1 oil in many different vsicosities. I run 10w-30 in the winter (here in Pennsylvania) and switch to 15w-50 for the rest of the year.<p>Andy Hedin<br>'97 A4 1.8Tqms....