I've got a few questions, so please forgive me for the long post. Here it goes.. 1.) I ready that regular Mobil1 is not fully synthetic, but the M1 Extended Performance is a fully synthetic oil. Is this correct? 2.) I am currently running M1 5W-30 in my 08 5.3L Silverado with a M1 filter. I am wanting to try a Wix filter at my next oil change and had a question on whether I should run a Wix or stay with the M1 filter. When running regular M1, should go with a Wix filter or stick with the M1? If I use the Exdended Performance, should I stick with the M1 filter or us a Wix filter with both. Currenty with using the M1, I go about 7,000 miles between changes, if I use the EP, I would go longer so I don't knwo if that would make a difference on which filter I use. 3.) Last question. My girlfiend has a 2005 Audi A4 1.8L. I want to run M1 in her car but didn't know if there was a better oil that is recommended for her car. I'm not sure if I would go with the full synthetic oil or no (most likely will though) and if I would use a Wix or M1 filter. Again, sorry for the long post in advance but I figured it would be better than creating 3 different posts. Thanks in advance for all the help guys.