PCV Valve?

[AZRedhawk44]

So, about two weeks ago I changed the oil, checked tire pressure and replaced the PCV valve in my truck.  Oil wasn't absurdly old, it was about 2000 miles and 4 months.  Tire pressure was around 22psi per tire, took it up to 32.  Makes sense it was low... I mostly ride the bike and leave the truck alone, and the temps dropped about 25 degrees recently here in AZ.

I was complaining about the transmission in this truck about a month ago here, and I know this has nothing to do with the transmission at this point, but fuel economy went from about 15.7 highway to 18.1 highway.  Just from those three things in the last 2 weeks.

I have a hard time believing that tire pressure accounts for 1.4mpg, or nearly 10% improvement.  Maybe on a sedan that gets around 25mpg or more.  So I figure I got maybe 0.5mpg from the tire pressure, max.

Can the PCV valve cause that much of a loss in fuel economy?  My understanding of how it functions is it grabs unburnt vapor from under the cylinder head cover and channels it back into the air intake.  The old one didn't seem to be too dysfunctional... supposedly the check for these things is to shake them.  If they rattle, the valve still works.

[dogmush]

Tire pressure makes a bigger difference then you think, and 22 psi is pretty damn low.

[Hawkmoon]

Tire pressure makes a bigger difference then you think, and 22 psi is pretty damn low.

Agreed. I'd guess that about 97.3 percent of your improvement was due to the tire pressure.

[zxcvbob]

Tires.

[Jim147]

Air pressure.

The old "super gas saver tune-up" was to over inflate the tires.

PCV? Let's not talk *expletive deleted*ing PCV!

I spent seven hours last night replacing valve cover gaskets and fixing the hose to my PCV. I have to pull the intake to get to the valve covers or the PCV on my vehicle. 

While a bad PCV can hurt mileage, the oil blowing out is a bigger problem when they fail.

jim

[AZRedhawk44]

I hear ya, but I check the air in my bike tires weekly, and my truck tires every month or two.

What ends up happening here in AZ is everyone gets a 5-10 psi drop when we finally shake off the triple digit heat.  Size of the psi drop just depends on how frequently you check your tire pressure, and the temp extremes between checks.

My truck has pretty much spent the last 2 months un-driven except for a very small handful of errands.  I probably used half a tank of gas in it in 2 months.  I topped it off 2 weeks ago when I did the oil/air/pcv maintenance, and I still have half a tank despite the fact I've been driving it a lot deliberately.  Tire pressure was in the 30's earlier this summer but I just haven't driven it or cared to check it since maybe August or so.

[Ron]

Do they play around with fuel blends seasonally out there? Better mileage with a summer blend in colder temps?

Here in Chicagoland I see a big drop in gas mileage as the temps cool off. I've heard that we get a winter formulation gasoline that can account for some of the drop in mileage.

 

[AZRedhawk44]

Do they play around with fuel blends seasonally out there? Better mileage with a summer blend in colder temps?

Here in Chicagoland I see a big drop in gas mileage as the temps cool off. I've heard that we get a winter formulation gasoline that can account for some of the drop in mileage.

 

We get a higher corn-likker blend in the summer, here.

[Brad Johnson]

Definitely tire pressure.  My Vic was, and the truck is, extremely sensitive to tire pressures below 35 psi.  If I let the pressure in the truck drop to 32-33 it will knock a full mpg off the economy (I run them at 40 psi).

Brad