First of all. The Amazon price for this item is 40% of what other big automotive web-retailers charge. Someone is trying to make excess profits.
On installation into my Ford F250 with V10, there is noticeable difference in the throttle response. Engine is more responsive to small throttle changes just above idle, and it seems less throttle is needed to ease away from a stop. There is less burble in the exhaust note. An added plus is that 1st to 2nd gear shift cannot be felt now (from less throttle needed?). Perhaps these plugs are more consistent at firing lean mixtures in newer cars. Note that old plugs removed have gaps still at factory spec.
One caveat - the differences may have resulted with ANY new plugs put in. New plugs with sharp edges at electrodes should start firing at lesser voltages compared with rounded electrodes on well used plugs. The exotic materials used in these plugs may make differences in extended term performance. Bosch (4504) HGR9DQI Platinum IR Fusion Spark Plug, Pack of 1
I gave my 99' Chevy Venture a tune up, with these plugs and a Bosch set of wires. after installing (which a pain on this van b/c I had to take off the intake manifold to get to the other bank) I took it out on the freeway and was astonished. My van could accelerate much faster than before with faster response. Gas mileage was the same, but that was solved my changing the O2 sensors.
I purchased these plugs as they were at a great price and the description says that it works for my car (2001 Mustang GT). When I went to get them installed the mechanic told me that the plugs will not work for my car as they will burn too cold and not pass smog here in California. I checked with another mechanic and he concurred. I wish I would have known about this issue before I purchased them. Be wary if you have the same situation as these plugs may be of no use to you.
Do not buy Bosch Plugs. I just got these for my 07 Ford Focus. The old plugs were original and had 99K on them, they were really worn out. These new plugs look cool and are supposed to be a huge upgrade over factory plugs. There is no upgrade, I think it's a bit of a downgrade even from the worn out factory plugs. The factory plugs look to be NGK iridiums. The whole 4 prong thing is stupid hype and does nothing to increase power or performance.
The car appears to accelerate a bit smoother but slower. And when decelerating at faster speeds the engine appears to "misfire" because you can feel it "shimmy".
I can't believe I wasted 30 some bucks on these pieces of junk.
This is the second time I have been burned by Bosch Plugs, they were junk in my 01 Civic too.
Replaced in to my 2005 HONDA Cr-V. Smooth engine firing and acceleration power immediately noticeable. I monitored the fuel consumption, before and after installation. I found out that fuel efficiency went down, understandably, due to "increase" in power. See below:
Before installation: 19.99 MPG (average)
After installation: 18.54 MPG (average)
where MPG = miles per gallon of 87% octane gasoline.
Overall..happy with the new performance.
This part (4504) does not fit my 2006 Mercury Mountaineer.
I checked the "fit your vehicle" very carefully and it says this part will fit my vehicle. It doesn't.
I should have gone to the manufacturer's website and checked their compatibility list.
Now I see that my vehicle isn't even listed in their database for spark plugs.
I guess this is one of the hazards of ordering through the web - the Amazon website says "it fits" when it doesn't.
I'm sending them back, but what a PITA.
Now I can't trust Amazon's website so I have to do a bunch of research myself or just buy stuff locally.
"Buyer beware!" - Bosch'
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