This is a question I hear all the time — "I just got a new Tundra and I want to treat it right — should I use synthetic oil? If so, should it be full synthetic or synthetic blend?" Unfortunately, the answer is complicated. Generally speaking, because synthetic oil has fewer impurities, better properties at high temperatures, slightly better viscosity, and it is more resistant to breakdown than regular oil, synthetic is better for AN engine. However, whether or not it’s better for YOUR engine depends on a few things.
To start with, do you follow the rules and change your oil regularly? If you're diligent in changing your oil, you'll probably never see one of the biggest benefits of synthetic oil. Because synthetic oil is resistant to breaking down over time or over under extended use, it's the best oil to have in your engine if you forget an oil change, or, if your oil changes happen more than six months apart. However, if you're changing your oil regularly and at the proper mileage you'll never be in a situation where your engine is at risk from worn-out oil. Evaluate your maintenance schedule to determine if you would benefit from synthetic oil use.
For example, think about a person who only drives 3,000 miles per year. They may go more than a year without changing the oil in their car. As oil ages, it's effectiveness decreases, and if it gets old enough it will break down and the motor will no longer be protected. In this case, synthetic is the logical choice. Also, if someone accidentaly goes past the recommended 5,000 mile oil change interval without changing the regular oil, it will start to "fall-apart" and the engine will be at risk. If you or someone you know might forget an oil change, synthetic is a good way to limit your risk.
If you’re good at changing your oil on time, there’s really only one other common reason you would want to consider using synthetic. As natural oil gets hot, it starts to breakdown. The longer it stays hot, the worse the breakdown. So, if you regularly operate your vehicle in such a way that the engine temperature is always high, you should run synthetic. For example: Letting your vehicle idle for hours at a time (like on a jobsite) will overheat the engine. Because you’re not moving, there is no high-speed air circulating around the engine to keep it cool. In this case, excessive heat can build and normal oil will break down. Also, constant operation in high ambient temperatures (like the desert) or at high altitudes (over 10k feet) will also lead to higher engine temperatures. High temperature desert air has poor cooling properties, and while the air above 10k feet is usually cool, it’s “thin” and also has poor cooling properties.
Synthetic oil is most often used in high performance vehicles. If you are utilizing your vehice like a high-performance car (high speeds, fast turns, you know who you are) then synthetic is a smart choice.
There's quite a bit of advice out their about using synthetic if you drive in a big city with lots of bad traffic, or if you only drive short distances. As far as traffic goes, it's all relative. If you're maintaining an average speed of 20mph in your commute, you're ok to run regular oil. As for the short distance advice, I can't stress enought that no oil will protect your engine from the damage of a three mile trip once a day. Engines are supposed to ran for a few miles before you shut them off, otherwise oil doesn't circulate properly and you will see premature engine wear. My advice to you is to drive farther if you can.
If you do decide that you would see some benefit from running synthetic oil, be conscious of “synthetic blends”. While many manufacturer’s have a synthetic blend as their standard oil, the term synthetic blend is not regulated. Any mixture of regular and synthetic oil is considered a blend, even if it’s just 1% synthetic and 99% regular. If it’s not a manufacturer provided oil (i.e. Motorcraft, Goodwrench, Genuine Toyota Motor Oil, etc.) then it could be a very low percentage of synthetic in the oil. Some companies will state the percentage, but you’d be surprised to find that big names like Valvoline, Penzoil, Quaker State, etc., have very low percentages of synthetic in their blended oils.
So you say that's all fine and good, but what do the people that MAKE the vehicles think? Toyota has no stance on synthetic oil, they only want you to use good oil and change it regularly.
Bottomline: Unless you’re subjecting your new 2007 Toyota Tundra (and the oil that’s in it) to extreme conditions, save money and use regular oil.