Diminished fuel mileage!?

Hi folks,
I have a 2012 Tundra 5.7 and it's got about 27k on it. I've had it for 2 years. Since day one I've averaged 15.5 mpg. The other day I checked and I'm averaging 10-11 mpg. The 30k service changes the air filter and checks pcv valve, but I can't believe that these two items would affect my mpg that much. The only thing that has changed is that I got new tires, OE size. Tire pressures are kept the same as previous tires. Any thoughts? Thanks in advance.

 

What's the outside temp where you live? Weight of the tires you got compared to stock? Just a couple thoughts..

 

Temps would be a non-issue since I've been in the same climate the whole time. Not sure of tire weight. OE tires were BF Rugged Trails, new tires are Bridgestone Blizzaks.

 

Own a flex fuel? Start towing or anything, I get 12.5 on avg and still have the tires from the dealer. 25k miles

 

This is what I was thinking. That's why I asked temp.. Letting it warm up.. And the yeti of gas the "winter gas or blend".

 

I suppose it's possible; but I've been buying gas at the same 3 stations all year long since I bought the truck. But 4-5 mpg less? I'm stumped!

 

Blizzaks are going to have a higher rolling resistance than the OEM tires, but I really don't think that would account entirely for the drop in economy that you're seeing. But I'm sure it's a component.

 

Mines went from 15 to 12.5-13 since the weather has changed, in any vechile I've owned every winter it does. My assumption is the winter blend fuel. Really the only explanation when it does back up in April or May.

 

I suppose that's likely; I just don't remember it dropping like that last winter. I'm trying to avoid letting the truck run to warm up when it's cold to see if that helps. I doubt it though, since it's actually been warmer this winter so far.

 

Winter blend with ethanol will take your mpg to nothing. Ethanol if mixed wrong at the fuel terminals can play games with ecms (retard spark) is one of them. The BTU ethanol is not as high as straight gasoline (fuel) for example. When you lower the BTU inside the engine the ECM see's it in turn the computer ( all ecms do it ) is to dump more fuel to get the BTU's up.. This is measured by your o2 sensors. Just because the engine temp is fine the pyro of the engine is a different story.

Depending on where you live the local state and even city code may require more ethanol in winter time in the fuel mix. i have seen up to 20% on ethanol in some places i could not image your mpg with that mixture.

Fyi if you live in a state that has high ethanol mixtures do your back account some good quit flooring it. it does nothing but empty it..

 

How are you tracking your MPG? By looking at the dash or manually checking it? I go on Fuelly.com to track mine and it seems my mpg is usually lower than what the dash says.
I would have to guess its the winter blend fuel though.

 

I got my truck in July and still average the 15 to 16.5 mph