Riptide

If I do decide to give the Amsoil 5W-20 XL a try will it void my warranty? I'm guessing not but I just want to be sure.

JimsGT

I'd go synthetic. I will be doing so at the next oil change. I'm wondering how much synthetic, percentage -wise is in the Motorcraft oil?
I think they do it because its cheaper than full synthetic, but the word synthetic is in there, so it sounds good! Although I'm not an engineer, I don't think it matters much that you have to use a blend.

When I got the airbag recall done, I had the oil changed, and the dealer asked me if I wanted to go full synth, but warned once you go full synth, you can't go back. Why would that matter? (BTW They wanted 65 bucks, I just had the blend put in, I'll go synth on my own).

I'm at 18k miles, I'm going to go to Mobil 1, just because its been around, and its easily available. I think all the synth oil brands are similar, and have to meet specs anyway, right?

Why would OHC motors like a blend better? Never heard of that...

I saw something mentioned of warranty, just keep your receipts of oil purchase. I was thinking that for awhile, keep going to the dealer because they're doing it, and its documented, bought the FRPP CAI/tune b/c is documented, etc. Tired of worrying about the friggin' warranty, going full synth oil, doing it myself, got a Steeda CAI/SCT custom tune, and I'm getting 3.73's in 2 weeks!!!!!

Matrix

Im pulling this outa my butt because I read it years ago and cant remember the exact details. Anyway, in the late 90s GM did a pretty thorough test on oils using Corvettes/engines as a test vehicle. They quickly determined that synthetics were superior to conventional oils and then set to determining which was the best synthetic. They started out with blueprinted engines that were as identical as you could possibly get them. Ran them thru identical conditions and then tore them down and inspected and measured everything. The winner at that time in their particular test was Mobil 1 5W30. That is when they started using it as factory fill in the Corvette. I also recall that they then tested engines withMobil1 with 5k mile oil changes and 10K mile oil changes and found no measureable difference. I believe some of the testing was on dynos and some in actual cars. The test is probably still out there somewhere if you really wanted to find it. I personally have been running Mobil 1 in everything since the mid eighties. This is back when synthetics were voo doo that would make your engine leak, smoke, have blowby, etc. Funny though when everyone would ask how my 85 Turbo Coupe had 165k on it with no trouble from the turbo.