I think my gas mileage is VERY bad...
please delete
08-23-2018, 08:21 AM
#2
Rennlist Member
You don't say how you drive it or what the mpg reads, or even what size tank you have. 981's should get ~30 mpg highway and ~15-20 mpg city depending on how hard they're driven in the city. It's actually quite good. 93 will get better mileage. I frequently get ~33 mpg highway with my 981S PDK.
08-23-2018, 08:54 AM
#3
Determine the mpg the old fashioned way. Fill up the tank, write down the miles traveled until next fill-up, divide by the number of gallons needed to fill up. There is always a possibility that a some electronic gizmo is not working properly.
08-23-2018, 10:58 AM
#5
Rennlist Member
08-23-2018, 11:11 AM
#6
Rennlist Member
https://www.planet-9.com/987-cayman-...-capacity.html
Possible that Cayman gets the 16.9 gallon tank, and boxster is 14? could be the reason you think it burns fuel quickly...
Possible that Cayman gets the 16.9 gallon tank, and boxster is 14? could be the reason you think it burns fuel quickly...
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08-23-2018, 11:44 AM
#8
If there haven't been any modifications to your engine and you are not seeing a CEL your gas usage is likely normal. If they did some ecu tuning before you bought the car you might have a gift coming from a retune to normal. Did the previous owner mention anything about "tunes"?
I would ask if a 20% extension of travel time between refills is worth it, might be, Whatever you decide, I'd give the car some time to acclimate to your style of driving and you to the car's, there might be a little interpretation on both sides that improves the mileage.
Lastly, as a suggestion, if you are doing relatively short city commutes, take the car out for a highway trip from time to time, a half hour or more of freeway speed will help the car's longevity.
I would ask if a 20% extension of travel time between refills is worth it, might be, Whatever you decide, I'd give the car some time to acclimate to your style of driving and you to the car's, there might be a little interpretation on both sides that improves the mileage.
Lastly, as a suggestion, if you are doing relatively short city commutes, take the car out for a highway trip from time to time, a half hour or more of freeway speed will help the car's longevity.
08-23-2018, 11:53 AM
#9
Does the car have sport exhaust and sport plus mode? I find that whenever I engage these, my gas mileage goes in the toilet. However the fun factor goes up exponentially! 
08-23-2018, 01:24 PM
#13
Rennlist Member
Yeah, I'm getting like 14 point something. Bad! I guess it's LA traffic.
As for the others, I don't think the previous owner did anything. I also only have Sport mode (not sport +) and I leave it off (for the week days)
Guess I'm gonna have to suck it up and pay the price on gas costs.
By the way, what kind of gas do you guys use here? in LA, I have never seen 93 Octane. Most places have 91. Just curious what you guys use.
As for the others, I don't think the previous owner did anything. I also only have Sport mode (not sport +) and I leave it off (for the week days
)Guess I'm gonna have to suck it up and pay the price on gas costs.
By the way, what kind of gas do you guys use here? in LA, I have never seen 93 Octane. Most places have 91. Just curious what you guys use.
I use 93 but know it's not available in CA. I think the highest octane you can buy from regular gas stations in CA is 91.
08-23-2018, 02:09 PM
#14
If you are using the TFT trip screen for MPG, make sure it is set for option '1', as that is the average over the current drive (still takes two hours of being turned off to reset). Options 2 and 3 have much longer intervals. There is also a reset option and once the car is warmed up then stop and reset it and take a drive on an interstate highway when traffic is light (I know, LA). You should see over 30 MPG if the car is driven softly in eco mode (Non-sports or sports plus mode). For me, I get 34 MPG in my 981 base and 30 MPG in my highly modified Cayman S, both PDK. MT may get a little less on the highway due to 6 speeds and a numerically larger final drive ratio.
I bought a `14 Boxster base that was a Houston Flood car and on the trip home, last June, from the state inspection station, the trip mileage said I was gettimg only 9MPG!!! Over the next two weeks, I drove about 200 highway miles more and got the number up to 13 MPG. Finally I went through the menus and set the Trip settings to option '1' and the next trip showed 32 MPG. I then took it on a 50 mile trip and used the auto stop/start declutch mode to the max and got a maximum of 34.1 MPG. Nothing wrong with the car, just incorrect setup of the trip odometer. However, city driving nets me only 21 MPG.
V6
I bought a `14 Boxster base that was a Houston Flood car and on the trip home, last June, from the state inspection station, the trip mileage said I was gettimg only 9MPG!!! Over the next two weeks, I drove about 200 highway miles more and got the number up to 13 MPG. Finally I went through the menus and set the Trip settings to option '1' and the next trip showed 32 MPG. I then took it on a 50 mile trip and used the auto stop/start declutch mode to the max and got a maximum of 34.1 MPG. Nothing wrong with the car, just incorrect setup of the trip odometer. However, city driving nets me only 21 MPG.
V6
08-23-2018, 02:19 PM
#15
One other point. If the battery goes flat or was disconnected, the adaptations in the DME (Engine computer) for the fuel system are lost and have to be re-learned over a short amount of time (15 minutes?). During this adaptation time, you can get really bad gas mileage.
You can also get bad gas mileage if the O2 sensors are contaminated via leaded gas (unlikely in CA unless the car was tracked and track fuel was used), or someone put in an octane booster with MMT in it, but that takes a while to affect the O2 sensor and MMT additives or similar may be banned in CA.
There was a vehicle campaign for the instrument cluster that was about inaccurate fuel mileage and gas level indications. After it was applied to my car, indicated highway mileage dropped about 1.5 MPG.
How many miles? Spark plugs should be replaced at 40K miles. Mileage may suffer a bit if the car has exceeded that. Photos that I have seen of 9A1 engine spark plugs changed at 40K+ miles showed a lot of electrode wear.
V6
You can also get bad gas mileage if the O2 sensors are contaminated via leaded gas (unlikely in CA unless the car was tracked and track fuel was used), or someone put in an octane booster with MMT in it, but that takes a while to affect the O2 sensor and MMT additives or similar may be banned in CA.
There was a vehicle campaign for the instrument cluster that was about inaccurate fuel mileage and gas level indications. After it was applied to my car, indicated highway mileage dropped about 1.5 MPG.
How many miles? Spark plugs should be replaced at 40K miles. Mileage may suffer a bit if the car has exceeded that. Photos that I have seen of 9A1 engine spark plugs changed at 40K+ miles showed a lot of electrode wear.
V6
Last edited by Voyager6; 08-23-2018 at 02:40 PM.