msmetz

I recently called the dealer and asked about the spark plug change. They informed me they are changed out at 100K miles. I just picked up the service manual and it says 100k KILOMETERs not miles. Which is 60k miles. So which is it? I just turned 70k miles and my gas milage has dropped so it may be time to change them out. Also the Bosch plat + 4 is cheaper than the NGK stock plug.

parula

My LEXUS Owner's Manual Supplement has spark plugs replaced at 120,000 miles with a note because of the terms of the emission control warranty. That is the ONLY reference to plug change I can find in the owner's manual. The Supplement does NOT recommend plug replacement at 60K miles. My Supplement is only miles.

On the other hand the dealer reminder schedule has replacing plugs at 60K and 120 K, presumably miles as that is when the 1K and 5K are called in here, not in KM. Wonder why?

ederny

ms,

No need to change the plugs at 60k miles unless you suspect a problem. 100k miles should be ok, 90k if you want, what ever is convenient. Use exaclly what Lexus specifies for this engine!

Consider this when you think about gas milage: you always burn more in colder weather (like we've been having). I have observed this in two winter seasons with the RX 300. That is, milage can drop, in my case from 23 MPG on summer highway trips to 17 MPG in the dead of winter on 15 mile trips to from work when temps are in single digits.

Why? You have probably already guessed - much more fuel is used to warm the engine to operating temp (warm up idle is higher and lower gears are held longer on shifts when heating up at thems below 30 deg).

I believe the above are the major factor. Others have also tried to convience me that the oil is thicker in the winter and uses more engery to push it around in the cold temps (yes, but a small effect). Also, grease in bearings (wheels, differential, transaxle, etc. is stiffer), yes, some loss here too. Tires are stiffer and rolling resistance is increased using more fuel. The air pressure in your tires is lower at cold temps and further increasing flexing of the tire. Driving through air that is cold is thicker (not too sure if this is measurable ?). There may be other reasons too.

I would wait to see if May hasn't restored your milage, and then use a bottle of techron and make sure your air filter is in good shape.

BOWTIE 3

The spark plugs used in all newer Lexus vehicles are the " IRIDIUM SPARK PLUGS ". The electrode tips are made of Iridium, which is a very hard material and supposed to last about 100,000 miles. I don't recommend leaving ANY spark plug in an ALUMINUM cylinder head that long. If no ANTI-SEIZE lubricant was used during installation the chances are high that the plug would seize to the threads in the head and head-replacement would be costly. Even if you're not replacing the plugs I recommend removing them and applying an ANTI-SEIZE lubricant on the threads and re-installing them. The Lexus dealer here charges about $20.00 each for new Iridium plugs; I get them at NAPA [ Denso or NGK ] for less than half that. This is the dealer that wanted $450.00 to replace all of the brakepads, not including machining the rotors. I bought premium pads at a local import auto store for under $60.00 and replaced them myself in about 3 hours. Although I'm a service-tech at a Chevrolet dealer and own a Silverado truck I don't think there is a GM vehicle made that compares in ANY catagory to my wife's RX 300! If Toyota built a REAL truck I'd NEVER own another GM vehicle, PERIOD! The Tundra is a bit too small and suffers from an UNDER-ACHIEVING engine.

parula

Bowtie, yes plug/block adhesion is apparently a real issue at least from what I have seen from several sources. I don't see anything in the dealer service schedules about it, does anyone? Do you think the dealers are resetting them routinely at 30k services anyway?
This seems to be an issue of which everyone needs to be aware.

msmetz

I just ordered a set of plugs from advanced auto. The NGK iridium was $6.99 so I orderd them. I looked at the old plugs and they looked ok, but I am going to change them anyway. They were not seized but they were a little tight. Access to the rear plugs was not as bad as I expected.