My ranger had a bent rod. Had to get a new small block. Installed it with the original heads. Truck runs great but I use to get 330 miles on a tank. Now I'm getting around 220 miles. I have a 3.0l. Why is my gas mileage so crappy after installing new block?

 

Most motors require a "break-in" period before you start seeing "normal" numbers when it comes to performance

 

And MPG you can expect your mileage numbers to be low for the first 1-2k miles. My ranger was the same way got 18 mpg for the first 2k miles then slowly went up to 35 on the highway.

 

Where'd you get your work done? I see you're down the road from me....

 

who did they work. if proper break in procedures are not followed you may not get a very good engine as a result. all the internal parts need to be broken in properly to seat the piston rings to the cylinders for proper compression seal. if there is a problem somewhere along the way you will get bad fuel mileage and power as well as a shorter life expectancy out of that engine

 

I did the work myself and I worked at a base hobby shop. I just installed the same heads on their and when the job was done I put in regular 5w20 oil and changed the oil after 500 miles. Then I changed the oil again and ran it for about a1000 miles and noticed the rear main seal was leaking so I put some rear main seal oil in it but it did not help. I have to replace the rear main seal now.