New Gas Cap & Gasket

[lexus082]

I recently decided to buy a new gasket for my gas cap since its recommended by toyota to have it replaced after ten years, so I did. I just bought the entire cap assy. which includes a new gasket on the fuel cap.

I believe my gas mileage has increased with the new gas cap. On a full tank of gas I just got about 440 miles to the tank. I was impresses with that. A couple of weeks ago I also removed my spare tire to see if there was any increase in fuel economy (which there was). And in addition to removing the spare tire I also noticed a gain of maybe 20 miles to the tank from the new gas cap.

Fuel economy before these changes 380-390 miles/per one tank of fuel.

---Removing spare tire (50lbs) 410-420 miles/tank.

---Installing new fuel cap & gasket 435-440/tank

*Mileage was recorded when gas tank was near empty (between 1/2- 1 gallon remaining), so I might have been able to get a few more miles, but I didn't want to run out of gas.

Driving style didn't not change 3/4 highway miles 1/4 city, average highway speed 70-80 mph, at times accelerated hard and I'm not a slow driver (moderate-heavy on the pedal at times)

Also, when refueling I noticed that when I removed the new gas cap there was no built up pressure like before with the old cap? Not sure why that was. No pressure behind that cap at all and I was very low on gas when I refueled. Before with the other cap there was alot of pressure being relieved when I removed the gas cap.

Based on my recent experience I would replace your gas cap gasket or just the whole cap assembly. If I remeber correctly it was only a few bucks more for a whole new cap verses just the cap gasket. If fuel economy decreases for some reason I will post an update. I don't expect it to though, the results were from several tank fulls of 93 octane gas.

[bartkat]

If you keep finding things like that, pretty soon you'll have to stop sometimes and drain out some gas.

[SKperformance]

You may be not actually experiencing higher gas mileage but keeping more of the gas in the tank rather than it evaporating .That would lower your overall MPG with the car still suing the same amount of gas.

[95_SC400]

I recently decided to buy a new gasket for my gas cap since its recommended by toyota to have it replaced after ten years, so I did. I just bought the entire cap assy. which includes a new gasket on the fuel cap.

I believe my gas mileage has increased with the new gas cap. On a full tank of gas I just got about 440 miles to the tank. I was impresses with that. A couple of weeks ago I also removed my spare tire to see if there was any increase in fuel economy (which there was). And in addition to removing the spare tire I also noticed a gain of maybe 20 miles to the tank from the new gas cap.

Fuel economy before these changes 380-390 miles/per one tank of fuel.

---Removing spare tire (50lbs) 410-420 miles/tank.

---Installing new fuel cap & gasket 435-440/tank

*Mileage was recorded when gas tank was near empty (between 1/2- 1 gallon remaining), so I might have been able to get a few more miles, but I didn't want to run out of gas.

Driving style didn't not change 3/4 highway miles 1/4 city, average highway speed 70-80 mph, at times accelerated hard and I'm not a slow driver (moderate-heavy on the pedal at times)

Also, when refueling I noticed that when I removed the new gas cap there was no built up pressure like before with the old cap? Not sure why that was. No pressure behind that cap at all and I was very low on gas when I refueled. Before with the other cap there was alot of pressure being relieved when I removed the gas cap.

Based on my recent experience I would replace your gas cap gasket or just the whole cap assembly. If I remeber correctly it was only a few bucks more for a whole new cap verses just the cap gasket. If fuel economy decreases for some reason I will post an update. I don't expect it to though, the results were from several tank fulls of 93 octane gas.

Was this an OEM lexus gas cap or a $10 replacement from an auto parts store?

[lexus082]

Correct, either way my mileage off of one tank has increased with removing the spare tire and the new gas cap. Also, it is a oem toyota/lexus gas cap that i bought. The part number for the fuel cap assembly w/ new gasket is 77310-14090. It was about $13.00 at Park Place Lexus. Its also a good toyota part number and you can pick it up at a toyota dealer probably cheaper than if you went to the lexus dealer.

[LEXIRX330]

Correct, either way my mileage off of one tank has increased with removing the spare tire and the new gas cap. Also, it is a oem toyota/lexus gas cap that i bought. The part number for the fuel cap assembly w/ new gasket is 77310-14090. It was about $13.00 at Park Place Lexus. Its also a good toyota part number and you can pick it up at a toyota dealer probably cheaper than if you went to the lexus dealer.

Real stupid question. What happens if you get a flat?

[jbarhorst2]

OK experts out there.

What is the proper situation?

Are you supposed to have pressure in the tank when you remove the cap or not?

Mine also releases a lot of pressure when I remove the cap. Maybe I need to replace mine as well??

Thanks for the help.

Tom

[lexus082]

If I get a flat I call a tow truck, I have towing insurance so I wouldn't need to pay the towing bill. Not a stupid question, not the smartest thing to do (remove spare tire), I admit. But if I'm saving $12/week in gas its worth it to me even if I did get a flat. ( I drive a lot.) I'll take my chances. Also the towing insurance has already saved me a lot more than what I pay for the towing insurance and the premium has not increased. I wouldn't recommend to others to remove your spare tire unless your comfortable doing so. Most of my driving is only to and from work.

That is a good question, whether or not there should be any pressure behind the cap or in the tank with a new gas cap installed?

UPDATE: Auctually, when I was refueling and removed the cap there was pressure and it sounded the same as with the old cap so I guess this is normal. Previously there was no pressure when removing the cap, but this time there was.

[blownsc400]

the fuel system in any vehicle is sealed and therer is pressure in the system to keep the fuel from evaporating. when you are low on fuel the pressure is not there any more because the fuel pump is pumping itss little heart out. so that swoosh is vaporized fuel that hes evaporated. hense the term, " your riding on fumes."

[mobilyte]

that's not pressure, it's vacuum that's created in the tank. you start off with a tank full of gas and zero air, use up the gas and the original quantity of air is left in there to fill the remaining volume.

if you dont agree, put your hand near the gas cap when you unscrew it at the station, you wont feel air blowing against your hand. likewise, you can hold a small piece of paper near the cap as your unscrew it and see it get pulled towards the filler neck.

[lexus082]

Well vacuum/pressure either way I would still recommend changing the cap or just the gasket. Seems like my gas gauge does not drop as quickly as before.