New car break-in

I bought a new 08 Tacoma, V-6, 4X4 last September. I put 900 miles (75-80mph driving) on it immediately on a PHX-LA weekend trip.

After brousing thru the owners manual, that was the LAST thing I should have done. Now at 3K miles, I’m getting poor (15-16 mpg city/hwy) gas milage. Did I screw something up?

edmunds reports that the v6 4x4 is rated for 16/20, plus it’s winter time so there’s more ethanol mixed in with the gasoline for winter driving, so what you’re getting is about right.

I doubt if you damaged your new truck. You may have aged it a bit, but I can’t imagine you doing so much damage that there would be a noticeable reduction in mileage.

I would suggest that it is far more likely that the cold weather and winter blend fuels have caused any reduction you have seen.

How did you measure that mileage and what does the EPA estimate for your mileage?

BTW with a new car you should drive it straight home and spend the evening reading the manual. Great stuff in there.

If you are really concerned have someone do a compression test on it. Is it using any oil? How much (quarts per miles)

There is LESS ethanol in winter blend gasolines. That is because ethanol is extremely hard to ignite once the temperature drops below freezing.


You’re not the only person who’s ever done this. While it’s not the way to break in a new engine, I don’t think it has anything to do with the fuel mileage you’re getting. 15-16 combined city/highway sounds like it’s about normal to me. Maybe slightly low, but not much. 4WD trucks are not renowned for their gas mileage. I had a 4WD Ranger a few years ago that never got better than 15 mpg. My '07 Ranger 4WD is currently getting about 18-19, but I have yet to see 20, and I’m not sure I ever will.

Agree that you have probably put about 10,000 miles of wear on it by going too fast. The reason for the gentle break-in is to gradually get the rings and bearing “seated” properly so the engine will not consume much oil over its normal lifespan. If the vehicle consumes oil after the first 2000 miles, you can blame it partly on uneven breakin.

I think you’ll be fine because most of your break-in will have occurred before you left on the trip IMHO. A little variation in speed on the highway also helps whether it’s going uphill, passing, or making stops, etc.
The mileage is within EPA specs for the 4X4 so you’ll have to live with that.

You haven’t put enough miles on the vehicle to break it in yet. Once you get 3,000 miles on it, you will be getting near your final gas mileage rating. You take a risk when you drive a new car that fast before things loosen up. If it didn’t overheat, maybe there hasn’t been any damage done. Don’t have anything tested and don’t go telling the service department at the dealer.

Owners manual is a recommendation not set in stone.

Everything sounds normal, enjoy your new truck.