Introduction:
Fluid Replacement Intervals:

Fluid	Normal Life	Extreme 1
Engine Oil	7,000 mi.	3,000
Transmission Auto	20-60,000	12,000
Differential (Rear-end)	30-60,000	12,000 2
Transfer Case (4WD)	30,000
Engine coolant	75,000 or 5 yrs.

Note: Many people recommend changing engine oil every 3,000 mi. or 4 months even if they are driving under extreme conditions. 1. Extreme Driving:

• frequent short (< 5 mi.) trips
• Dusty conditions
• Trailer towing
• off-road driving
• 50% of your driving at high speeds is during hot (> 90 deg) weather

Fluid Levels:
Overfill Oil:
At the Tundra forum (http://www.tundrasolutions.com/forums/engine-and-drivetrain/) they said:
"If the oil level is extremely high and reaches the crank it can make the oil foam resulting in a LOSS of lubrication and make your engine labor harder with the extra oil.
A quart of oil only raises the level in the crankcase about 1/4.
An extra quart and one half won't cause a problem."

One person said "Excess oil can contribute to higher pressures and excessive vapors in the crankcase and could cause leaks as the extra oil is forced past seals and/or gaskets.", but most think that foaming is the only problem.

Most modern engines run with a slight VACUUM in the crankcase, which is maintained by the crankcase breather valve and PCV Valve (I am not sure but I think our Tundras us a Variable-FLow PCV Valve). However, the crankcase CAN become "PRESSURIZED" (at least in theory) due to a clogged PCV valve (which I am sure you know that the VAPOR from HOT engine OIL and also from exhaust gases escape past the piston rings via the PCV valve. If this "blowby" exceeds the ability of the PCV valve to draw in the vapors, the excess blowby will flow through the breather hose to the air cleaner housing where it then re-enters the combustion chamber (Not trying to give you a PCV Valve101 lesson.
Having said all that, THE THEORY IS THAT THE INCREASED OIL CAN LEAD TO INCREASED "BLOWBY" WHICH IN TURN CAN LEAD TO A CLOGGED PCV VALVE AND/OR BREATHER VALVE. A plugged PCV valve can make your truck run richer, BUT a clogged breather hose could possibly cause the engine to consume oil because of the INCREASE in the crankcase vacuum.

A Lexis owner reported his dealer added new oil without draining the old. Afterwards, everything seemed fine, but I noticed that it was putting out lots of blue smoke, especially under hard acceleration. I checked the engine but couldn't find anything wrong. I took the car back and told them about it. They didn't seem real concerned. They checked the engine out thoroughly and reported that everything was fine. I guess it was, becase I drove it another 15,000 miles and had no problems. So I suppose a measly half quart overfill won't make any difference.

See:
Antifreeze page