The 4.5L Diesel Tundra – Does It Make Sense?

Update: Read the complete story of the diesel Tundra

For the 2010 model year, the rumor is that Toyota has decided to take the 4.5 liter diesel engine that currently resides in the Australian LandCruiser 200 and shoehorn it into the Tundra. Given that each of the ‘Big Three’ domestic truck makers has committed to offering a diesel engine in their half-ton trucks, this move is designed to help put Toyota on equal footing as well as raise the CAFE fleet fuel economy rating for the Toyota brand.

The 4.5 liter diesel engine that will be used in the Tundra is brand new for 2008 in the LandCruiser 200 (Australia’s version of the Land Cruiser). A direct injection V8, it produces 286 horsepower and a stunning 480 lb-feet of torque in the Australian market. These numbers should be quite similar once the engine has been altered to meet U.S. emissions standards. In the LandCruiser 200, the 4.5L diesel is mated to a 6-speed automatic – one very similar to the Tundra’s current 6-speed matched to the 5.7L, so that feature will undoubtedly carry over to the U.S.

The 4.5L diesel features a twin-turbo setup to keep the horsepower up for highway cruising and as well as low-end power for towing. The use of a twin-turbo system in a diesel is new for the U.S. market – the diesels in most trucks feature only a single turbo (except Ford’s relatively new 6.4L Powerstroke). However, with ever more restrictive U.S. emissions standards, twin turbo diesels will probably become more common.

At first inspection, the purpose of the half-ton diesel is a mystery. The current diesel options – the Ford Powerstroke, the GMC Duramax, and the Dodge Cummins – all generate about 350 horsepower and a very serious 650 lb-feet of torque. The Tundra’s 4.5L diesel can’t hope to offer similar performance, which begs the question – What’s the point of this engine?

The answer – fuel economy. Diesel engines typically achieve 25% – 30% better fuel economy than a normal gasoline engine. Diesels are naturally more fuel efficient because they do a better job of retaining heat generated in the combustion process (reducing heat loss), they run at much higher compression ratios (thermodynamically better), and they generate lots of power at low RPMs (lower RPMs equal less fuel use). Early estimates are that the 4.5L diesel engine will achieve an average of 22-23mpg in the Tundra – quite a bit better than the average of 16-17mpg that many Tundra owners are currently getting with 5.7L.

Some have said that buying a diesel Tundra half-ton, even one that gets 22-23 mpg, doesn’t make a lot of financial sense. First of all, diesel maintenance is more expensive. Diesels use a lot more oil, they tend to use more fuel and air filters, and diesel fuel is currently more expensive than gasoline. Secondly, there’s an up-front cost premium associated with the diesel – we’re guessing the diesel Tundra will cost about $3,000 more. For some buyers, the diesel Tundra’s better fuel economy may not be enough.

While there is some truth to this argument, it’s important to remember that diesel engines last twice as long as gasoline engines (on average). That means the diesel Tundra will have much higher resale value than a gasoline-powered Tundra. Also, the actual cost difference between diesel and gas engines will very much influence the final calculus. If the cost premium for a diesel engine is less than we’ve estimated (say $1,500 instead of $3,000), the diesel’s improved fuel economy will quickly cover the higher maintenance and up-front costs.

In the final analysis, there are quite a few reasons to be excited about the diesel Tundra. For one, the presence of a diesel motor in the lineup with gobs of torque on tap will likely attract a new range of buyers who want to be able to tow their animal trailers and boats without sacrificing fuel economy. Toyota diesels, and diesel motors in general, are also known for their great reliability, and combined with Toyota’s pre-existing image for build quality, the diesel should become an attractive option for work truck buyers. Lastly, there’s no denying that a twin-turbo, diesel powered Toyota Tundra will be cool as hell.

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