Here's a novel. The girlfriends Volvo has a screen/ vent under the oil fill cap, which appears to be covered in sludge. The dipstick doesn't have any particles on it though. Is it a safe assumption that the engine could have sludge in it? I imagine the turbo isn't helping anything either. Right now she has her oil changed religiously every 3000 with Valvoline Maxlife, but her car is short tripped to death. She gets it changed at a dealer for about $20ish plus tax (with coupons), but I am wondering if a synthetic oil would be better? Since her car has the cartridge filter, I cant help but wonder if they skip that occasionally too, which could also contribute to the dirty engine. Apparently a few years back they got on her because the filter was in such poor shape.. Dirty engine or not, I cant imagine it looking that bad at 3000 miles. JMO. PP/ PU and a TG/ Ultra cartridge filter for about 3000 miles until it appears clean?