I use 0-40 mobil one in my street cars and 15-50 mobil one in the race car. I have used synthetic since the mid 80's. It is very common for an older vehicle to use oil when first switching to synthetic, don't worry about it. It will stop using oil before you need your next oil change. I'm not sure if any synthetic is better than the other one. I used Amsoil untill about 5 years ago but Mobil was more available to me.