Some basic ones to start with.
1. Change the oil - Every car in GT5 benefits from a oil change, more so the older second hand standard cars. But, even the new cars need regular oil changes. My premium Audi R8 Chrome Line dropped power from 877hp to about 817hp after a coupe hundred k's. I changed the oil and it went back up to 877hp!
2. To get the most hp out of a car, don't be afraid to drive it and drive it often. Example; my Veyron after mods had about 1220hp. After many races and regular oil changes, the engine is now producing 1232hp! My Red Bull Nascar produces more hp than a standard one also because of this.
3. Check the engine rebuild option in maintainance often to see if repairs are needed. A barely worn engine will cost as little as 500cr to fix, but leaving it for ages and could mean a rebuild cost of 50,000cr! (pending on the car of course). Same could be said for body rebuild, but I don't how much of an affect ridigity has in this game.
4. Always go for Tier 3 turbo and exhaust upgrades. Don't bother about buying Sport's or tier 2 exhaust/turbo etc upgrades unless you are aiming for specific hp target, or if the tier 3 exhaust note is horrid! A few cars I run tier 2 exhaust simply to improve the sound! Of course, weight reduction and engine tuning has to be done in the three allocated stages.
5. Check the Used car dealer regulary as the list is updated with new listings often, removing older listed vehicles. I had the chance to buy some awesome looking BMW Le Mans race car, if I wasn't 1mil short of the 3.7mil price tag. By the time I get enough money, it will be gone from the list
6. Don't be like me and buy every car from the 40's, 50's 60's, 70's, and 80's in the Used car lot... costs a fortune and you end up with a garage full of old classic's that never get driven!
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