Originally Posted By: lexus114
but how may of you guys are using conventional oil in a vehicle that recommends synthetic?
Good question, most of us would probably use the correct synthetic oil required. Mostly it's an indirect synthetic requirement because the oil that meets the OEM spec only comes as a full or semi synthetic e.g. dexos or VW 505 or MB 229.3 etc.
However I live in a warm climate with no cold start issues, and in Australia I can get conventional oils like Castrol GTX 15w40 that are rated SN and ACEA A3/B3. I think it's easier for a heavy mineral oil to meet the more difficult specs like Euro A3, than a lighter mineral oil.
So yes, if I had a Mercedes that was out of warranty, and required MB229.3 (for example) and I was short of cash but had lots of GTX 15w40 A3/B3 in my oil stash, then yes I would probably use the A3 GTX mineral oil. But I would change the oil much more frequently, say every 5000 km or 3000 miles. With the oil filter every second (or third) oil change.
But if I wasn't short of cash, I would buy the correct synthetic oil.
BTW Shell Helix HX7 10W-40 semi-synthetic is SN, A3/B4, VW 502 / 505, MB 229.3 and is as cheap as chips at KMart and would be my first choice of non-full-synthetic.