Brake switch fixed Cruise - MPG lower than my right foot.

[PatDTN]

I had to put a brake light switch in my new to me '09 Tahoe LTZ to fix the cruise control. It's got the 5.3 Flex engine.

Until then I had been managing with my right foot and with a mix of highway and a little city driving was right at 19 mpg on the average for two tanks of gas.

I had about 50 miles on this tank and the average was at 18.7 when I finished putting in the switch. Now after driving some of the roads that I found increased my mpg it's down to 18.1.

There are some interesting things about cruise control and this beast. One of the first things I tested that I had only sort of felt was the grade control. Nice to cruise down a hill and have the Tahoe downshift to keep my speed.

Going up several long grades I drive regularly I found if I left it in Drive there was no way I could hold a speed I wanted. It would start lugging down and I would push harder and harder on the gas. Suddenly it would get the message, unlock the torque converter and downshift at least one gear then take off liike a scalded rabbit. Easing off the gas gently as I approached the speed I wanted it would lock up and shift back up until it couldn't hold the speed again. With cruise control it manages things and holds nicely steady. I guess I could have popped into manual shift mode and dropped a gear...

 

[STORMIN08]

Cruise control unless on a dead flat road, usually will net less mileage.

The timing variable to adjust to speed allows it to over throttle to regain mph quickly thus fueling harder.

 

[PatDTN]

Cruise control unless on a dead flat road, usually will net less mileage.

The timing variable to adjust to speed allows it to over throttle to regain mph quickly thus fueling harder.

Yeah, I know. I just sorta thought it would even out on some roads that were fairly flat but I guess even "fairly" flat I can anticipate hills and it can't.