This little story will hopefully act as a warning in time for someone not to have to spend what it's costing me! :-( RV = Georgieboy Landau 3301, 1999, 6.5 V8 Turbo Diesel, 30,000 miles. We've had the rig for 4 years now and she's been a belter. Runs smooth, 13mpg which considering we're loaded up fulltimers I'm happy with. ALWAYS change my own oil and filter.......just cos I enjoy it. ALWAYS buy from West Midland American Vehicles (Delco filter, Morris Oil) and NEVER had problems. However......... :-( This year, before the French holiday, I had a filter to fit but no more oil and not enough time to go down to Dave's at Cannock and get the same oil. So, armed with my Chevy handbook, off I trot to the local car shop where i buy COMMA oil at the right grade and the correct spec acording to what's on the can and what's in my handbook. Did an oil change and we're off to France for 2 weeks where we do 2500 miles down to the Pyrenees via Loire and Dordogne. Bus runs a treat until, halfway back home, we pull off the Autoroute for a brew after a continous run that morning of approx 200 miles at a steady 60 in not particularly hot weather. Came to fire her up.......THUMP THUMP THUMP, back through the air filter!!!!!!! HELL!!!!!!!! Thinks I, What's up? says ffiona. I recon that an intake valve isn't closing properly and allowing back pressure into the intake manifold. So, after a couple of gentle probing tickles on the throttle, she quietens down a bit but you can still here it in the background. I've no warnings on the christmas tree, no smoke, no loss of power, no nothing. So, do we chuck her straight on an 18 wheeler, or do we risk it and watch the dashboard like a hawk? !!!!!!!!! We risked it, and thankfully she got us home to our "base" site in Cheshire with no further drama. So, we book her into West Midland and after a good look, Ivan (the mechanical geneus) say's "when was the last oil change?" "two weeks and 2500 miles ago before the holiday" said I. "NO WAY!!!!!!" says Ivan, "the oil came out like sludge" So, i showed him the can with the left over oil, "HONEST" I said, "I DID change it." Basically, the oil had sludged up in 2500 miles!!!!!!!! Why? I don't know. The oil brand is the ONLY thing that was different and i KNOW that COMMA oil has been going for donkey's years, they're an old established company. BUT, again, the oil brand is the only thing that was different and even tho it met the spec, i recon it just couldn't hack it in a big 6.5 litre diesel. The oil sludged, the camshaft lifter (follower) jammed, the push rod jammed into the end of the lifer, the valve wouldn't close properly and thus, i got back pressure. The head is now off and being machined and at least one new valve fitted (the lifter and pushrod-which have already been done, didn't cure it). GOD ONLY KNOWS WHAT IT'S GOING TO COST!!!!!!!!!!!!!!! :-( No jam on my butties next month, that's a dead cert.! :-( ..........and all down to a bad choice in oil..........at least I recon. Be carefull what you put in your pride and joy guys!