fuel syste cleaner

Don't use any fuel cleaner in the tank. It's not needed and you could damage the tank bladder. The colder weather is probably causing the lower MPG. Also check your tire pressures. If you take short trips, your MPG will definitely take a hit as the ICE needs to run more to warm up and to keep the cabin warm.

 

44-45 MPG isn't bad in cold wet winter weather. The ICE runs more to keep itself and the catalytic converter hot to keep emissions low. Tire pressure drops with the temp, as firepa says, so make sure they're at 40 psi front/38 psi rear, at least. If you really want to, you can add Techron to your tank, but you shouldn't have to use more than regular gas at any time.

All cars get worse milage in the winter, but a Prius has instrumentation so you know it. Happy driving, welcome to PriusChat! :welcome:

 

If by "midgrade" you mean 10% ethanol, it could be some of your problem. Ethanol blends contain less energy and you get lesser mileage. I recall the owners manual recommending regular grade fuel. I get fewer mpgs whenever I put ethanol in anything in the driveway.

I wouldn't think a fuel system cleaner would be a problem for the fuel bladder. You would only need to run it once or twice a year.

 

Ditto that, it's almost certainly the cold weather. Remember to check tire pressures monthly or more often. Some of us use 42/40 PSI front/rear which gives a harder ride but allows better MPGs.

Octane greater than 87 is a complete waste of money in a Prius.

The ethanol you already get in your gasoline is a fine engine cleaner. Don't risk screwing up the fuel tank bladder by using any kind of additive.

 

Re: fuel system cleaner
Here is what I received from an inquiry to Chevron regarding Techron Fuel System Cleaner ..............

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From [email protected]

Dear DOC;

Thank you for your inquiry concerning the use of Techron Concentrate Fuel System Cleaner in your 2004 Toyota Prius. Although after investigating the matter we have no reason to suspect that Techron will harm the bladder in your fuel tank, we regret that we have not discovered solid proof, confirmed by special tests, that the material in the bladder is compatible with Techron.

We contacted Toyota and learned from them essentially that that the bladder is composed of materials commonly expected to be inert to fuels and fuel additives. However, Toyota did not provide any test information that could be used to confirm the compatibility of the bladder with Techron. Chevron has tested Techron with a variety of fuel system materials, and confirmed compatibility with Techron for most vehicle fuel systems. However, we haven’t tested the Toyota Prius bladder; so we don’t have specific test data on it to confirm compatibility with Techron.

We are sorry also for the time taken by our investigation, which resulted in a delayed response to you.

Sincerely,

Chevron Fuels Technical Service