vs
Spark plug Autolite or OEM BMW
I changed the spark plugs to Autolite Double Plat plugs from Autozone. The smoke cleared up and it is MUCH easier to keep cranked in the cold (30's F) in the morning. It still has a very light stumble every few cycles and a louder engine idle than I'd like, but runs good and seems to be much better.
Pros: smoke cleared, easier cold crank, runs good
Cons: light stumble, louder idle
Vehicle:
Volkswagen Passat B6
I installed a set of Autolite 3923's gapped to .032 and guess what? FIXED! unbelievable, after all this testing only to find out that all I needed was new plugs.
Pros: problem fixed, unbelievable result
Vehicle:
Volkswagen
Mileage: 172199 km
Part number: 3923
So, I went ahead with the Autolite XP iridium plugs. Right now, I cannot complain. Everything is running pretty good. I put these in to compare to the standard Autolite copper plugs that I put in my 2001 2.0L AEG in January of 2009. Here is what has happened so far. 1. Since the new plugs, my idle rpm increased about 50-100 rpm to low 800s to mid 800s . Whether this is good or bad, I don't know. This may consume a small bit more of gas though while sitting at a stop light. 2. Since the new plugs, I can also feel a small vibration that seems to come from the engine bay. This only happens on a cold start as I am accelerating from around 15-40 mph. When it's warmed up, it's gone while accelerating. This may come my new catalytic converter and flex pipe that I just got installed, but I don't know. It may also come from new front rotors and pads that I just put in that haven't had time to properly be bedded, I don't know. I am putting some new dog bone mount inserts in within the next few days as well. 3. Since the new plugs, my engine seems to have had a small performance increase in acceleration, response, and in smoothness; except in cold start accelerations as stated above. This may not make a big deal to some, but I am happy with this. 4. Since the new plugs, the best deal I have had is the lower rpms when I am using cruise control around 40-55 mph. I am serious when I tell you that my rpms went down a good 150-250 rpms at these cruising speeds. I do believe that because of these plugs, I will get a small boost in mpg; I will let you all know shortly. Also note that only the plugs and nothing else was changed at this interval. Can I tell you what happens at 65 mph+, no because I don't go on a highway to school or work. So, my overall impression with the iridium plugs is a positive one so far. I have gone just over 500 miles since the new plugs were put in.
Pros: improved acceleration, smoother engine, lower cruising RPMs, potential MPG boost
Cons: increased idle RPM, cold start vibration
Vehicle:
Volkswagen Jetta
Mileage: 805 km
Good old standard Autolite Coppers work just as well as anything on the market, as long as you replace them every few thousand miles. At $.99 a piece, you can't beat 'em.
Pros: good performance, excellent value
Cons: short lifespan
Autolites last as long for me as the NGK's. Either of them last about 10k miles for me. Any longer than that and I start getting missfires. The Autolites can be found for about $1.00 each
Pros: last 10k miles, cheap
Cons: misfires after 10k miles
Mileage: 10000 km
Once we got a good local supplier for Motorcraft plugs a few years ago we almost never install Autolite.
Pros: good local supplier
Cons: almost never install
There seems to have been quality issues with those for quite a while. I couldn't count how many times we removed fairly new Autolite spark plugs and replaced them with a better brand to fix a misfire.
Pros: fixes misfire
Cons: quality issues
I wouldn’t put autolite plugs even in my lawnmower. NGK or Denso only.
Do not get Autolite, I've seen them cause trouble and issues in Honda engines.
Cons: cause trouble, issues
Vehicle:
Honda
Yesterday, I installed new spark plugs in my 2004 TJ. Going off [this thread](https://wranglertjforum.com/threads/what-are-the-best-spark-plugs-for-my-jeep-wrangler-tj-4-0.4196/) I purchased the Autolite XP985. Originally, I gapped the plugs to .04 based on [this thread](https://wranglertjforum.com/threads/spark-plug-gap-for-4-0.17415/). The jeep ran terribly and actually threw a check engine light.
I went back today and changed all the gaps to .035 based on the note under the hood, but I still think the idle is a bit rougher then what it was before the change.
Cons: rough idle, check engine light
Vehicle:
Jeep
Part number: XP985
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