# 2012 Highlander MPG down 40%! **URL:** \ **Category:** Power/Fuel\ **Tags:** toyota\ **Created:** [November 23, 2024, 9:13pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131 "2024-11-23T21:13:18Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![cshams](https://avatars.discourse-cdn.com/v4/letter/c/71e660/32.png) [@cshams](https://community.cartalk.com/u/cshams)\ **Post date:** [November 23, 2024, 9:13pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/1 "2024-11-23T21:13:18Z")
Hi everyone, I’d love some help. Over the last year, my 2012 Toyota Highlander Limited (95k miles) MPG has rapidly diminished MPG. We drive mostly in the city, running errands and picking up kids with occasional trips up to the mountains for skiing and 2x/year 1,000 mile roadtrips. About 10k miles per year on average. The vehicle is rated 20/25 mpg city/highway. Since we are mostly city driving, we experienced ~18-19/mpg. Over the last year, mileage has been diminishing to the point that it is ~12 mpg (40% lower than rated!). I took the vehicle to our local repair shop in early October, and they did the following: - Replaced spark plugs - Fuel induction service - Replaced air filters (engine and cabin) - Alignment Nothing has changed! Mileage is still at about 12mpg. Any thoughts on what might be happening, and what I can do about it? Thanks! Make: Toyota Model: Highlander Limited AWD Year: 2012 Mileage: 95k, give or take ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [November 23, 2024, 9:17pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/2 "2024-11-23T21:17:13Z")
Here’s a few nitwit (i.e me) diy’er ideas: - faulty coolant temp sensor - faulty o2 sensor - faulty intake air temp sensor - exhaust system problem Has your shop done a fuel trim test? ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [November 23, 2024, 10:10pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/3 "2024-11-23T22:10:59Z")
Give some ideas about the maintenance history. Have you followed the Toyota rec’s from the owners manual? How do you check on your MPGs? The only sure way is to track mileage and gallons over a good long time (at least a few full tanks) and do the math. If you’re just looking at what the computer says, that’s usually pretty reliable, but you want to check up on it. Is/has the check engine light been on? If so, then the shop would have read the codes and they should be on your receipt. With or without a check engine light, like @George_San_Jose1 implies - someone needs to put a scantool on it and check things like coolant temp readings, O2 sensor behavior, air temp readings, and look at fuel trims. So some idea of what the shop did and said beyond just replacing parts would be nice. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [November 23, 2024, 10:27pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/4 "2024-11-23T22:27:03Z")
Dragging brakes? ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [November 24, 2024, 6:09pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/5 "2024-11-24T18:09:43Z")
Clogged cats. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [November 24, 2024, 6:52pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/6 "2024-11-24T18:52:56Z")
Bad thermostat not letting the engine get up to temp. ---
**Author:** ![Clueless33](https://avatars.discourse-cdn.com/v4/letter/c/dbc845/32.png) [@Clueless33](https://community.cartalk.com/u/Clueless33)\ **Post date:** [November 24, 2024, 7:43pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/7 "2024-11-24T19:43:54Z")
Ensure your tires are inflated at recommended factory setting. My Lexus IS was suffering from exactly what you described here and my first thought was tire pressure because my car is up to date with maintenance. Now I’m achieving reasonable MPG again. ---
**Author:** ![FoDaddy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/fodaddy/32/717_2.png) [@FoDaddy](https://community.cartalk.com/u/FoDaddy)\ **Post date:** [November 24, 2024, 7:59pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/8 "2024-11-24T19:59:51Z")
> [@cshams](#): > > The vehicle is rated 20/25 mpg city/highway It is not. It’s rated for 17/22 MPG > **[2012 Toyota Highlander 4WD](https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=31994)** > > Fuel Economy of the 2012 Toyota Highlander 4WD. Compare the gas mileage and greenhouse gas emissions of the 2012 Toyota Highlander 4WD side-by-side with other cars and trucks You were quoting the fuel economy figures for the FWD 4 cylinder. The was no four cylinder available with the Limited trim or AWD. 12 MPG is still low for the vehicle. 18-19 MPG is indeed what you should be getting in everyday mixed driving. I would check the easy stuff first; tire pressure and making sure there isn’t a brake dragging (it should be fairly noticeable when your car is coasting). You might want to see if there are any stored codes present as well. If the check engine light is on, it could cause the engine to run in open loop, which would cause an increased in fuel consumption. ---
**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\ **Post date:** [November 24, 2024, 8:33pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/9 "2024-11-24T20:33:15Z")
> [@FoDaddy](#): > > You were quoting the fuel economy figures for the FWD 4 cylinder. The was no four cylinder available with the Limited trim or AWD. > > 12 MPG is still low for the vehicle. 18-19 MPG is indeed what you should be getting in everyday mixed driving. Indeed. While I take the self-reports to fuelly with a grain of salt, they usually seem to make sense. [Average based on those is just shy of 19, though 19 is the mode.](https://www.fuelly.com/car/toyota/highlander/2012?engineconfig_id=&bodytype_id=&submodel_id=61) ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [November 24, 2024, 8:33pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/10 "2024-11-24T20:33:36Z")
+1 to all of @FoDaddy’s comments, but I also want to remind the OP of a possibility that was previously mentioned, namely a cooling system thermostat that is stuck in the open position, causing the engine to run too cold. The OP mentioned in his first post that this condition has been going on for about 1 year, and that causes me to wonder if the diminished gas mileage began around the same time as the mounting of a new set of tires. If there was a new set of tires mounted around that time, did the OP verify that they were a low rolling-resistance tire, similar to the OEM tires? If not, that is another factor that could account for a drop in gas mileage. Also, is the OP _sure_ that his motor oil is of the viscosity specified by the vehicle mfr? If his mechanic has been using a “thicker” (higher viscosity) oil, that could also account for a drop in gas mileage. ---
**Author:** ![davesmopar](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/davesmopar/32/41750_2.png) [@davesmopar](https://community.cartalk.com/u/davesmopar)\ **Post date:** [November 25, 2024, 12:20am UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/12 "2024-11-25T00:20:53Z")
Never mind ---
**Author:** ![Purebred](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/purebred/32/46796_2.png) [@Purebred](https://community.cartalk.com/u/Purebred)\ **Post date:** [November 25, 2024, 6:41pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/13 "2024-11-25T18:41:41Z")
I doubt tire pressure is a factor. If the OP has been loosing air from their tires for a year, I think it would be visibility noticed. They had an alignment done, would the shop not inflate the tires to specifications? I hope the OP comes back with some answers. ---
**Author:** ![Cavell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/cavell/32/43396_2.png) [@Cavell](https://community.cartalk.com/u/Cavell)\ **Post date:** [November 25, 2024, 7:46pm UTC](https://community.cartalk.com/t/2012-highlander-mpg-down-40/198131/14 "2024-11-25T19:46:07Z")
What does trip computer say? Reset it. Drive around. I believe computer.