My coolant light comes on when I turn on the car and immediately goes away as soon as I start driving. Thing is, I've noticed that my fuel economy has decreased by about 1 mpg. Now I'm curious if there is a correlation between the two??

I'm going this afternoon to go buy some coolant, probably Prestone because that is what I have found mostly mentioned when I searched on here.

 

Nope, and use FL-22 if you can. The coolant light commonly fails but it could just be that you are low on coolant. Can you give us a history on the car?

 

Has about 96.5 miles, bought in July 05', runs great, never seen the coolant light until this winter. The coolant light has been doing this for about a week. I'm assuming we can get FL-22 at Autozone or Walmart?

 

Oh also, I usually get about 290 to a tank, all hwy driving, 90 miles a day, usually 22-23 mpg. But recently, its at like 20-21. Perhaps the cold weather could be a factor to take into account when calculating MPG.

 

Well at 95,000 I would say it is the coolant level sensor (common issue after many miles). If this is the original engine I would take it to the dealer for a compression test since the warranty on the engine is only until 100k. I got my engine replaced at 96,000. Are you losing coolant? If so, then it coudl be a bigger problem if there are no coolant leaks easily spotted.

 

No. It's Mazda's own brand. Need to go to Mazda. If your radiator cap says FL-22, and you believe the 10 year/100K claimed lifetime, you should use that. It's glycol (like Prestone) but already diluted...I think 55/45.

When I bought a jug of the stuff the parts guy had a blank look at "FL-22." Then when I said "coolant" he said "Oh - the green stuff." If your coolant is green, make sure you use green. If it's orange, use orange. If you mix the two it still works, but supposedly turns black.

As far as the coolant level light goes... it is my belief that the factory that makes those is built on the site of the Pet Semetary, and there is no rational explanation for what that light does.

Ken

 

Thank you both for the info. I will be going to the dealer regardless because I just received my letter from Mazda for the clutch bracket.

But I was curious, is there any possible relation between the coolant light and the slight decrease in mpg? I understand it could be a wide array of factors such as tire pressure, weather, way i drive, etc, but I haven't changed anything in terms of my driving style.

I just filled her up so I will see how this tank turns out..

 

I wont call 1mpg difference is a big change.

 

i seem to have misplaced my owners manual, but the collant light is right next to the oil pressure guage right? kinda looks like a little white house lol. anyways mine has been doing the exact same thing your describing, turns on cold starts then turns off when driving, but recently its been staying on all the time now. and i cant believe you can get 290 to a tank, im lucky to get 220, and i mainly drive highways as well, with the occasional city but for the most part just cruising at 75-80

 

If the coolant is leaking into the rotor housings (think blown head gasket on a piston engine) then yes it will affect mileage. But if your coolant is not low then that is unlikely. If you have coolant in the driveway then you have an external leak.

 

yeah... and actually mixing green and orange makes it into a slushie.... very very bad

 

You must have the mpg really dialed in if you notice a ONE mpg difference, lol.

 

Yeah I'm very **** about it haha. I usually get 290-300 which I am very happy with for this car. So when I see that it's only getting 280, obviously I would question it. But i filled her up with a new tank, so we shall see how this one turns out.

 

So car was parked overnight in garage, turned her on this morning and no coolant light. I haven't done anything to her so I wonder......I'll see tomorrow morning if it turns on.

 

1 mpg is just about a couple extra rpm on a couple shifts on a tank

 

So new tank was 282. That divided by 13.3 = about 21.2 mpg. Now that is not a DRASTIC difference from 22, but questionable to me.

The interesting thing was when I went this morning to refill, when the pump clicked to signal that tank was full, it read that it had stopped at 13.055 gallons. I did not dare pump further because I feared overfilling even though it should be 13.3 gallons.

Reasons why pump stopped before 13.3 gallons??

 

Where are you getting 13.3 gallons? I believe capacity is 14.9. My best tank was 305 miles but I filled up with like 14.4 gallons so i was pretty much bone dry.

 

I might be incorrect, but as soon as the fuel warning light comes on, and I go to pump gas, it clicks at about 13.3 gallons. I know it can go more, but I assumed overfilling was not smart. So I'm confused....

 

The fuel tank size is 15.9 gallons

 

Just add a little coolant. I've had that too...

 

Reasons why pump stopped before 13.3 gallons??


Because your gas tank was full. Why should it have stopped at 13.3?

 

I recently completely flushed my coolant (let it drain completely and filled it back up) but I only put in a 1 gallon jug of the OEM FL-22 stuff. Same thing as you; my light came on when cold but then went away once the car warmed up (coolant expands). The manual says the car uses about 2 gallons so I just added some more until it reached the "full" mark on the coolant tank.

Don't run low on coolant though, it can create cavitation in the water pump and possibly cause some issues.

As for the mpg's, I think its just due to the low temps,. I went from 200+ miles per tank (mostly city driving) to about 150. And if anything, my driving has been less fuel demanding than before.

 

Why is 21.2 questionable to you? When you got the 21.2 mpg did you drive the same exact places/rpm/idle/speed as you did when you got 22mpg?

 

I've got 22.5 mpg recently traveling over 300 miles before the red light came on. Now the temperature has dropped below freezing and I will be lucky to get 160 mi on this tank. The climate affects mileage too.

 

That is what I also suspected to be the culprit, but quite wasn't sure.

And the reason I fill up to 13.3 gallons is that as soon as the fuel light comes on, I'll go fill her up and it says 13.3 gallons on the receipt. I know it can go more than 13.3, but when it clicks, then I assume that I'm good to go.