Does grill block reduce engine oxygen intake?

Odd how blocking the grille reduced your fuel economy. With my 2004 Prius, it generally helped, especially in temps <0 F

Like most modern cars, the Prius doesn't draw any intake air from the grille area, but from the fender

It could be a coincidence, but remove the grille block and see if that returns fuel economy to normal. There could also be a mouse nest in the intake piping somewhere, and be sure to check the air filter housing by removing the air filter

 

doc is correct. It should not reduce oxygen supply to the motor, but it should assist with engine warm up time. It keeps the cold air from blowing directly in on the engine compartment. I seriously doubt that is what is affecting your first 5 min. bar. Did you block upper and lower grill? I have blocked mine ever since I purchased the Prius, and have never had any trouble whatsoever.

 

IMO the blocked grill isn't the cause. You said it's colder now. That's the cause. In moderate temps I don't see much of a difference & expect 25mpg for the 1st 5 minutes & 50mpg for the next 5. Even with the grill blocked some winter mornings I wouldn't be surprised to see minus mpg. After the 1st 10 minutes you should see some improvement & green bars more often. Over the winter you may find that the lifetime average was maintained instead of decreased but this is very dependant on the OAT.

 

Wow, where is it colder now? Here in the "great white north" we're having a hot "Indian Summer". It's supposed to get up to 30C today (about 80F), about as hot as it gets even in summer!
Grill block is the furthest thing from -my- mind.

But yes, as the above posters have said, the upper grill block will not decrease the engine's air supply, nor will the lower grill block. The engine breaths from just in front of the passenger front wheel. And I've also never seen a decrease in fuel economy from grill blocking. It -should- improve it slightly as it would lower drag a bit. But probably not enough to see.

 

I tried an upper grill block for the first time and had no improvement in fuel consumption over earlier in the winter. I removed the grill block and my consumption improved by 0.1L/100km. I don't know why.

 

Unusually hot here too. This time of the year, I'd have the A/C turned off and covered up. We're getting our July weather a bit late, but at least we're getting it

That's odd. I would usually start grille blocking once the temps were around -10 C consistently. I do know that at -30 C and colder, the grille block makes a big difference in comfort

 

I have all top grills blocked and 3/5 from top to bottom of the bottom grill blocked. It is about 40F in the morning and gets up to about 70F highest in afternoon. I drive about 45-60 mins on rolling hills at around 40mph. I don't have any temperature monitor, is this going to get my car too hot or can I go ahead and block another bottom grill?

 

Without any way to monitor temps, I'd hold off blocking more of the grille until the temps got colder. I never even started blocking the top grille until the temps were consistently -10C

 

I improve greatly when I only do about a 50 % block and even run it in the summer. I block the lower half of the top (chrome section) and then 3 slits on the bottom year round. Most of my trips are about 20 miles. I pull all the lower block off if I plan on driving long distances at highway speed or if its unusually hot (+ 90 degrees) meaning I will have more A/C use. My rule of thumb is that if the radiator fans click on its time to pull some off.

 

getting close to the time of year where i would start blocking as well, but forecasts are for the mid 80's next week so putting that idea on hold for now.

 

Could it be that cold here is 4 C minimum and max of 13 C?
Day time temps here lately have been 12 C to 21 C.
We had a couple of days over 25 C so I removed the grill block, I doubt I'll be putting it back in.

 

Sorry Pat, we don't call +4 C "cold" in this country. In Spring, we call it "summer"

 

We had 3C the other morning, and it's still summer for another day or 2

 

We're getting our July weather right now, have had highs in the 30's, lows of 10 C and warmer.

Back in July, I still was using heat. I felt like sparking up my gas fireplace early

 

On the 15th of August it was 28 C here. That is over 2 weeks inside winter here.

 

the fan does come on supposedly at at relatively low temp. but i had not heard it run for YEARS. but only because i jus had not been around it.

this past summer, i heard it run, but was hardly an event. the scenario, OAT was 101 º F.

had driven about 30 miles one way on freeway, jumped off freeway because passengers with me had bladder issues. so, i actually hit the power button instead of the park button and figured, i turn it on when they came out. well we stopped at rest stop so it was an immediate off freeway and park thing.

well, about 2 minutes after the car was turned off, the fan came on and it was relatively loud and very noticeable. well, it ran about 15-20 seconds and shutoff. was off like a minute. came back on, ran another 15 seconds and shut off that was it.

in retrospect, i can see why i never heard the fan much...it simply does not run that much. didnt have scangauge on the Pri at the time, but guessing water temp was probably in low 190's when running and spiked a bit when i shut down. during winter, my water temp is nearly always high 190's to low 200's and i never have heard fan run in winter. so apparently, the engine cools off pretty fast and i have verified that parking for as little as 10 minutes in relatively mild winter weather is enough to restart the warmup process