We always enjoy talking cars with the opinionated Alex Nunez from Autoblog, most recently last week when we both appeared on FoxNews.com's Fox Car Report with dapper host Gary Gastelu.

This week's guest was Derrick Kuzak, who heads up global product development for Ford. Meaning he's the guy responsible for the design of every car and truck Ford builds. Pretty great job, huh?

The first EcoBoost engine is a 3.5L petrol V6 with 355hp (265kW) and 350ft-lb (474Nm) of torque

The first EcoBoost engine is a 3.5L petrol V6 with 355hp (265kW) and 350ft-lb (474Nm) of torque

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

2010 Ford Mustang Shelby GT500 Convertible

ecoboost_tech_01.jpg

The 2010 Taurus SHO performance model will be the first Ford to offer the EcoBoost engine.

The 2010 Taurus SHO performance model will be the first Ford to offer the EcoBoost engine.

2011 Mustang motors

After the show, talk turned to rumors of new engines for future Ford Mustangs. Kuzak didn't spill the beans--he's always happily, insistently on message--but he advised us to pay attention at the 2009 Los Angeles Auto Show in December.

Our pals at Motor Authority says the 2011 Mustang is expected to get a pair of new engines: a new base 3.7-liter Duratec V6 with 315 horsepower, and a new 5.0-liter Coyote V8 with 400 horses.

And Nunez also noted rumors of an aluminum-block 5.4-liter supercharged V8 to go into the 2012 Mustang Shelby GT500, which he asked Kuzak about. Answer: "That's a good idea."

And how is this green?

We don't spend a ton of time talking about 400-plus horsepower engines here at GreenCarReports, but this all got us thinking. Minutes earlier on the show, Kuzak said that Ford would offer EcoBoost engines in 90 percent of its model lines by 2012.

EcoBoost, remember, is the combination of gasoline direct injection and turbocharging that gives a smaller engine the power of a much larger motor, but with higher gas mileage. Ford is all about EcoBoost these days.

Mustang + EcoBoost

Stupidly, we didn't think to ask Kuzak about EcoBoost for Mustangs. But afterward, we got to wondering: Which EcoBoost would you put into a 'Stang?

It wouldn't be the current 3.5-liter EcoBoost twin-turbo V6, which gives V8 power and towing capability with V6 fuel efficiency. That's the one now offered in the 2010 Ford Taurus SHO hot-rod sedan and Flex crossover, and the 2010 Lincoln MKS sedan and MKT crossover.

That engine wouldn't make much sense, since Mustangs are known for their V8s. If Ford ever stopped building V8s, you know the very last one would go into a Mustang, right?

So we came up with two alternative theories. We think each is plausible, but there are problems with each one too. Here goes.

THEORY I: Barn-burning EcoBoost GT500

Our counterpart Nelson Ireson of MotorAuthority suggests that what Nunez calls a supercharged GT500 engine is in fact a twin-turbocharged, aluminum-block "Road Runner" version that might rate as high as 600 horsepower.

Gee, twin turbos. Add direct injection, and what does that sound like? Might Ford plan to brand a high-end 5.0-liter V8 as an EcoBoost engine too? It could give all the performance of a barn-burning V10 (like the one in the Dodge Viper, say) but keeps gas mileage in V8 range.

Problem: Ford is positioning EcoBoost as much for its fuel economy as performance, and if there's one thing the GT500 is not known for, it's gas mileage.

THEORY II: Entry-level EcoBoost four

We also wondered about a new, entry-level Mustang with the recently announced EcoBoost four. That's right, a four-cylinder Mustang, something not seen since the early 1990s. But this one would actually be fun to drive.

Before you start shrieking about government regulators destroying the soul of the 'Stang, hear us out. The new 2.0-liter EcoBoost four, with a single turbocharger, replaces a standard V6 up to 3.5 liters. But it gets the gas mileage of that small four.

Suppose we saw a new base model Mustang, with a 2.0-liter EcoBoost four with equal performance to the previous 4.0-liter base V6, but giving more than 30 miles per gallon on the highway? That'd certainly skunk the 2010 Camaro's 29-mpg highway rating.

Problem: So far, Ford has positioned EcoBoost at the high end of each model line, so a low-end Mustang might not fit that image.

Caveat emptor

This is all just speculation, of course. Only Ford knows what it'll launch at the LA Auto Show; we mere mortals will wait until the designated hour. Or at least until it leaks onto the Intertubes.

But we thought it was worth throwing out there. Plus it gives us an excuse to put up some pictures of the 2010 Ford Mustang GT500, which we're fond of even though it's not [ahem] quite as green as we'd like.

Sooner or later, we're pretty sure there will be an EcoBoost Ford Mustang. So what do you think it should be? Tell us in the comments below.

[Autoblog via MotorAuthority]