Reading the gas gauge

The gas gauge on the Prius is commonly referred to as a "guess gauge". Due to the bladder in the tank, the gauge is non-linear and somewhat inaccurate. Your best approach is to fill up when you get down to 2 pips on the gauge. Running out of gas with the Prius is a bad idea.

 

Refill it now and see how much it takes. Keep a fuel logbook.

You first tank is not the time to push the low fuel limits on any car, and the Gen2 Prius is worse than others. Build up some history, watching how much fuel it takes at various gauge readings, before pushing lower. And watch for consistency. Gen2's fuel bladder is notorious for being inconsistent.

 

The rated capacity is 11.9 gallons. However, with the bladder, you probably won't get much more than an average of 10.5 gallons. Keep in mind that the bladder expands and contracts. So in hot weather you'll get more fuel in the tank than you will in cold weather.

This is a great site for Prius info: http://john1701a.com/

 

And just to add to this, if the bladder happens to be folded when you fill, then you may only get a few gallons in. Doesn't mean it is full to the max capacity, just means that the way it is currently shaped no more will fit from the top right now.

So don't play chicken with the gas gauge in the North American GenII.

 

I figured 1 gallon per pip. At 2 pips think about buying gas. At 1 pip buy gas. When the pip flashes BUY GAS NOW. You NEVER know how much gas is left but you'll know (too late) when it is empty.

 

Agree completely.

The most I've ever put in my Prius was 9.975 gallons. I think I was down to 1 pip but don't remember if it was flashing.

 

I had a bad experience while taking my car to Jiffy Lube and not sure who is at fault. May just be me. I never have heard that you should keep your tank 1/4 full at all times due to air getting in the fuel tank. After Jiffy Lube changed my oil, (I had one bar on the gas gauge and no warning light, no flashing, nothing), I drove about a block and all the warning lights came on: The Master Warning light, the Engine Check, the Hybrid System warning light, ABS, etc. I stopped the car. Started it again and the lights were there again. I drove back to Jiffy Lube and lost momentum the last half block. They tried to come up with some really lame reasons for it and I finally said let me get to my dealer. My gas gauge still had one bar and no warning there. Towed it in and was told that it was my fault as I let the gas get too low and it caused air to enter the tank. They spent 2 hours bleeding air out of it which cost me $200.00. I've never been told by anyone to keep the tank at 1/4 or more full or that this could even happen. Shouldn't I have gotten a warning light or something?

 

I refill with two (2) pips left. I add usually exactly 8 gal. just about 400 miles. Then first pip lasts approx 125 miles. next pip much less etc. I have never had a fuel issue!
Just avoid JiffyScrew like the plague. I had one clown leave a oily rag on the manifold of my 4Runner, The truck started smoking about a block away, U turn, and I drove right back into the JiffyScrew bay and had them put the fire out!

 

As written, I would call your shop's story a crock. This is not a requirement for cars in general. Air must enter the tank as fuel is pumped out in order to keep it from collapsing the same way an empty lightweight soda bottle, when sealed at the top of a mountain hike or pass, crumples in on itself on way down to sea level.

Many people do follow a common maxim -- not in the owner's manuals -- of never letting the tank get lower than 1/4 full. But that is for other reasons, some real, some common mythology. Many more of us ignore this maxim regularly, without consequence -- except for those who forget to refuel and run dry.

But your Gen2 is a special case due to its unique fuel bladder, and your issue could be a slightly scrambled version of its peculiarities. Past discussions have included mention of air getting in between the bladder and fuel tank wall, worsening the already poor accuracy of the 'guess gauge'. And there is something about fuel sensor calibration. But I don't have this model (the bladder was abolished in my Gen3), so must defer to other Gen2 owners for a better answer.

 

This is a ridiculous story. The fuel tank in the Prius picks up fuel from the bottom, just as with any tank. Air in the tank could create back pressure that would prevent you from getting a full fill-up, but it won't cause your engine to stop or generate errors.

Are you sure you didn't run out of fuel? That's what it sounds like.

Tom

 

No, I still had fuel. I started the car to move it out of the garage at Jiffy Lube in order for the tow truck to come and started it again for the tow company in order to move it again for him. It would initially have some engine power, followed by what would feel like simply loss of pressure and it would coast. I still had one bar on my gas gauge and no warning at all. I'm no mechanic, but this all has made no sense to me.

 

Even when I'm down to a blinking pip, I've never put more than 6.5 gallons in. Weird?

 

That is odd. The most I've ever put in my Gen 2 was 9.975 gallons.

Perhaps you should recalibrate your inclinometer. I've never done this as I don't see the need for it on my car. See http://priuschat.com/forums/gen-ii-...auge-calibration-instructions.html#post179565. Some gory details about the fuel system at the link pointed to by http://priuschat.com/forums/gen-ii-prius-main-forum/81725-fuel-bladder-question.html#post1142097.

 

The reason you don't want to run any tank low...is to prevent your fuel line from getting air in it if you run dry for a moment [which will also cause your line to soak in all the other sediment and nasty stuff at the bottom of the tank and then destroy your fuel filter and gunk up your stuff] and as well..fuel surrounding your pump will also help keep your fuel pump running cooler.

Fuel tanks are usually vented to the atmosphere [through a charcoal canister to remove the fuel scent]...otherwise like mentioned, pressure will build up inside of your tank and put additional stress on your fuel pump.

For instance I have a sumped fuel tank and can't let it drop below a 1/3 tank because starving my big external fuel pump even for an instance can be catastrophic, also when you have less fuel in your tank it will raise your fuel temperatures [if return style system] which will cause the car to run less than ideal.

Did they replace the fuel filter by chance?

 

Thanks, I'll have to try that!

 

On my 07 I routinely wait until I have 1 bar left and it is flashing before I refill. Almost always it takes in 8.5 gallons, only once did I get it to take over 9 gallons. I generally get about 400 miles range per tank driving around San Francisco, mixed driving.
Some times it will only take 6 gallons and my range is much closer to 300 miles.
I think the fuel bladder gets more negative press than it deserves.

 

This is what worked for me. Disconnect both terminals of the aux battery and touch the end of the cable together for 5 seconds. Re-connect the cables. This will recalibrate everything in your car.