I've changed the oil and filter on my volvo 940 turbo st wagon myselves for the last year. The car has done 150000 miles, mostly on highway, we are allowed to go 85 MPH and I always do. Manual says to change oil and filter every 10000 Miles and Shop always used a standard oil. It normally burns 1/5 to 3/4 liter of oil between changes. First time I changed it I used a BILTEMA ( our NAPA kind of store ) semisyntetic. Next change Penzoil syntetic and I observed less consumption. Last 10000 miles was with Mobil 1 syntetic on Lubedudes advice. Now I suddenly had next to none Oil consumption. Did any of you experience anything similar. The oil is still clean and light brown, doesnt look worn at all. Does oil difference really mean that much.
<br /><br />I drive an overloaded Ford e150 cargo van w/ 4.6 liter OHC with 186K on it. I've used 0w-30 synthetic since it was broken in at about 5k mi. My engine uses one quart of oil each 4.5 to 5k miles. I use a supplemental by-pass filter which I change, along with the OEM filter, every 25000 mi. I HAVE NEVER CHANGED THE OIL!!!! I simply add two new quarts at each filter change and that motor runs like the proverbial Swiss Watch.<br /><br />Now that's my opinion! 
