# Fluctuating Gas Mileage **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [June 2, 2007, 6:21am UTC](https://community.cartalk.com/t/fluctuating-gas-mileage/150 "2007-06-02T06:21:25Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![SJGUY99](https://avatars.discourse-cdn.com/v4/letter/s/d07c76/32.png) [@SJGUY99](https://community.cartalk.com/u/SJGUY99)\ **Post date:** [June 2, 2007, 6:21am UTC](https://community.cartalk.com/t/fluctuating-gas-mileage/150/1 "2007-06-02T06:21:25Z")
Last month I purchased a 1990 Oldsmobile Eighty Eight 2 Door with 54,000 miles. With the tank full, on my first drive around Phoenix with the a/c on half the time and driving normally, I got 13mpg. Then, I drive on the highway at a constant speed of 55mph (cruise control on) for 80 miles with the a/c off and get 20mpg. Then, I drove around Phoenx for 80 miles with no air conditioning and driving like a grandma, staying at the speed limit and at a constant speed as much as possible. I got 20mpg. Unbelievable. First, I get 13mpg in city driving with the a/c on half the time and driving normally, then 20mpg on the highway driving for 80 miles at a constant speed of 55mph cruise control, and now 20mpg around town driving like a grandma with no a/c. I’m totally stumped now. What’s going on with this car? I’m not making this up. I’m just perplexed. The only think I can think of is that this car is "breathing and opening up more. Maybe the highway drive “cleaned the car out.” The car only has 54,000 original miles.The man I bought it from was in his late 80’s who only drove in town to the store and church. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [June 2, 2007, 10:14am UTC](https://community.cartalk.com/t/fluctuating-gas-mileage/150/2 "2007-06-02T10:14:30Z")
I’m totally stumped now. What’s going on with this car? The only thing going on is you just found out that grandma knows what she is doing driving like that. She saves gas. It most likely is your driving. ---
**Author:** ![system](https://global.discourse-cdn.com/cartalk/original/3X/1/d/1d47c66a543aa6c5a7873bb2320858f978ff52ed.png) [@system](https://community.cartalk.com/u/system)\ **Post date:** [June 2, 2007, 4:44pm UTC](https://community.cartalk.com/t/fluctuating-gas-mileage/150/3 "2007-06-02T16:44:44Z")
Right, but by that toke, wouldn’t I have gotten more than 20mpg on the highway then?