Wednesday, July 22, 2009

Are V6's and V8's getting bad rap?

A fuel efficiency meter. (ex. At present, this...Image via Wikipedia

There seems to be a rush by auto manufacturers to introduce turbo 4's and turbo 6's to substitute for V6 and V8 engines, respectively. The INTENT was more fuel efficiency. In fact, some had earlier promised "Power of V8 with fuel economy of a V6". However, do they actually deliver more mileage? Or are V6's and V8's getting an unfair rap as fuel guzzlers?

Here's a comparison from Car and Driver mag (July 2009 issue, page 34)...

Nissan Murano vs. Mazda CX-7. Roughly same class of cross-over, yes?

Nissan: 3.5L V6, 265 HP, 248 LB-FT
Mazda: 2.3L Turbo I4, 244 HP, 258 LB-FT

Nissan enjoys a bit more HP, but Mazda gets more torque. However, keep in mind that there is a little bit of turbo lag for the Mazda, so Nissan should be peppier in city speeds. But let's call it equal.

Nissan: EPA 18/23, C/D observed: 23 MPG
Mazda: EPA 16/22, C/D oberved: 20 MPG

So the Mazda actually consumed MORE fuel on the average, despite having a smaller engine. Isn't that interesting?

C/D also shown that BMW 328i, with 3.0 I6, is more frugal than an Audi A4 2.0T /Quattro, which is a turbo 2.0L I-4. And MB S550 with 5.5 V8 gets better combined mileage than BMW 750Li, which has a twin-turbo 4.4 V8.

In fact, Ford had went on and admitted that their "EcoBoost" turbo 4's should get same fuel-economy ratings than the current unboosted V-6's.

And this is despite that fact that a turbo 4 should be LIGHTER than a V6, enjoys turbo lag (though that's reduced in modern turbos), has less torque band, will probably run hotter, and probably requires premium fuel.

So why should you buy a smaller engine that gets WORSE fuel economy (or at least, "no better"), than current V6's and V8's?

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