fuel enconomy - 986 Forum - The Community for Porsche Boxster & Cayman Owners

911sc · 10-04-2005, 07:25 AM

I like to know if anyone out there have the similar problem that i have ,today i fill up the gas to full tank and had only driving it for 8.8 km the fuel guage meter seem to drop a bit ,if i have to guese is should be around 3mm in gap ,i have driving it once with full tank to light on i am getting 400km is that sound normal ? it's 97 boxster ,is that normal only it's up to full tank? after a 1/4 tank than it seem to be okay ,which u don't notice in when down that quick when looking to the fuel guage ,appericiate if someone know this problem,thank's

MNBoxster · 10-04-2005, 10:22 AM

Quote:

Originally Posted by 911sc

I like to know if anyone out there have the similar problem that i have ,today i fill up the gas to full tank and had only driving it for 8.8 km the fuel guage meter seem to drop a bit ,if i have to guese is should be around 3mm in gap ,i have driving it once with full tank to light on i am getting 400km is that sound normal ? it's 97 boxster ,is that normal only it's up to full tank? after a 1/4 tank than it seem to be okay ,which u don't notice in when down that quick when looking to the fuel guage ,appericiate if someone know this problem,thank's

Hi,

There are really a several issues here. First, if the Car isn't level when you Fuel it, it can cut-off before the Tank is actually Full. Try this again at a different pump which seems level and see if it makes a difference. Second, there is some variation in the Gauge. It can drop more/less suddenly due to Temp, Barometric Pressure and voltage - not much variation, but some nonetheless.

Finally, when trying to determine range, you'd need to consistently drive the same route at the same speed(s), shifting points, weight, Head Wind/Tail Wind to determine anything with consistency. Even a long idle on one tankful will make a difference on your average. The OBC Hack will help alot as it constantly averages and recomputes the data. Hope this helps...

Happy Motoring!...Jim'99

JackG · 10-04-2005, 11:08 AM

If I understand your question correctly, I believe my Boxster does the same thing.

I can fill up on level ground, and I let the gas pump stop when it detects the tank is full. I know it is full, because if I try to pump any more gas, the tank overflows (done that twice, but no more!).

The gas gauge not only doesn't show completely full (it's just barely below the full mark), it also drops very rapidly. Within 90-100 miles, the gauge is down to just barely above 1/2 tank.

The last half of the tank goes much slower. It will last over 200 miles.

Bottom line is that the gas gauge is not accurate or linear. It could be the sender unit in the tank, or the gauge itself, but since I know how it acts, and I always reset my trip odometer when I refill, it's no big deal.

Jack

cfos · 10-04-2005, 11:15 AM

Hi Jack (and anyone else who has this issue) -- quick question(s) is your box also a 97? Or is this an issue that other people have with all 986s and 987s?

JackG · 10-04-2005, 11:46 AM

Quote:

Originally Posted by cfos

Hi Jack (and anyone else who has this issue) -- quick question(s) is your box also a 97? Or is this an issue that other people have with all 986s and 987s?

Mine is a 2000 S model.

Jack

TriGem2k · 10-04-2005, 01:06 PM

Sounds like everyone is getting decent gas mileage... Im lucky if i get 215miles per tank. Any thoughts. Never really thought anything was wrong. Is 215 miles per tank too low? I have a 2001 Boxster.

MNBoxster · 10-04-2005, 01:27 PM

Quote:

Originally Posted by TriGem2k

Sounds like everyone is getting decent gas mileage... Im lucky if i get 215miles per tank. Any thoughts. Never really thought anything was wrong. Is 215 miles per tank too low? I have a 2001 Boxster.

Hi,

Gas mileage is dependent on a number of factors. Your Driving Style, type of Traffic encountered (what mix of Free-Flowing vs Stop & Go), frequency of long periods of idling, terrain encountered, proper Tire inflation, frequency of use of AC, condition of Air Filter, condition of Motor Oil, condition of Brakes, quality and type of fuel, even if you drive Top Up or Top Down or using lots of accessories at once.

If you feel that your mileage isn't adequate, look into each of these things to see if any improvement lies there. Hope this helps...

Happy Motoring!...Jim'99

tqtran · 10-04-2005, 11:16 AM

same here, I just reset my trip counter and when it gets to 300 miles I go for a refill.

berj · 10-04-2005, 11:38 AM

I've got a 2005 987 and on the highway cruising at about 115km/h I can get somewhere in the range of 750-800km on a full tank. I've never actually let it go down to empty but I made almost 600km (Toronto to Montreal) on 3/4 tank. This is about 30mpg or 7.8 l/100km. The gauge seems to be fairly linear (ie about 100km travelled for each 1/8 tank, 400km for 1/2 tank, etc).

All this was with Esso 91 octane gas. I've started using Sunoco 94 octane but things don't seem to have changed too much as far as fuel economy is concerned.

In the city is another story, however. I'm getting somewhere in the range of 15-20mpg, sometimes less.

larez2 · 10-04-2005, 09:35 PM

I drive a 99' and get about 520km from full to when the light turns on and I drive pretty hard/fast. 400km until the light sounds kind of low under normal driving conditions. maybe you need a tune up? My light comes on after I've used about 14 gallons of gas.

I've seen the fuel guage dropping off fast or not going all the way full on other cars. It ended up being the sending unit that needed to be replaced. It's basically a thing that goes in the the gas tank with a float that gets pushed to the top when the tank is full and goes down when the fuel level goes down. But i did a search of the Porsche 986 catalog for "sending unit" and found nothing. So maybe it is called something different in the Porsche world.

HTH,
Larez2