Lpg Conversion - Maintenance Question - Spark Plugs Replaced Every X Km?

[blacksuitdandruff]

Hi, need an opinion here.

I have a 2010 Chevy Aveo that I LPG-converted about 9 months back. Cars been running great and saving me a lot of money on the fuel.

Went to the conversion shop today to do my 20K km maintenance. They changed the airgas filter (?) for a tad under 600 baht, but also wanted to change the 4 spark plugs.

They had already changed the plugs to NGK type (the yellow box - sorry don't have them in front of me) when they did the conversion.

I was a bit shocked that the price was a little 800 baht and that the shop recommended that they would need changing every 20K km. I inspected the 'old' ones that they looked and smelled fine though they were a little light brown on the tips. Also, compared them to new ones and the tips looked to be exactly the same length and width leading me to believe that there was little if any wear. So I passed on installing them, but have ordered online the same kind for so I can change them at home when needed.

I read on the internet that engine oil and spark plugs last longer on LPG converted engines but for some strange reason on this forum that seems to the contrary (one poster changed theirs every 10K km). Also, on petrol only cars, I've changed my spark plugs every 100-150K kms with little problem on comparable cars. I know the combustion temperatures are greater and the voltage required is higher on LPG engines hence a different type of plug and maybe why they need to be changed more often.

So question...if changing the plugs how many km is safe?

How many km is pushing it?

Lastly, what are the subtle starting signs that they need to be changed?

Thanks.

[WarpSpeed]

All things being equal I don't put specific mileage on changes I do personal inspections and also diagnose both mileage and operation. I give visual inspections along with performance impressions. If they put in Bosch Platinum or an equivalent you can get as much as 15 to 20k miles not k's, IMO they're selling you a load of goods, if you don't have any problems and the tips look good as you say and the color you describe sounds perfect for mixture IMO you're good to go..

I had multiple older LP cars and only changed plugs once in one that was misfiring a bit, the others were running just fine even when I bought and sold the cars with at least 15,000 miles on them and gaps still within specs. In that case I only had to keep an eye on the rotor and cap but the wires and plugs were virtually bullet proof and still running strong..

I'd say you could comfortably get another 5 to 10K out of them..

[blacksuitdandruff]

I only had to keep an eye on the rotor and cap but the wires and plugs were virtually bullet proof and still running strong..

I'd say you could comfortably get another 5 to 10K out of them..

Thank you for your input.

I agree that they were trying to over sell me.

I'll be sure to look/feel for misfiring.

[VocalNeal]

LPG does run a bit hotter and plugs do wear out faster, so use standard plugs I think about 80-120 baht each and change them every time you change the oil. Sure you can buy special plugs for 600-800 baht each but... that is 2400 baht for a set.

[blacksuitdandruff]

LPG does run a bit hotter and plugs do wear out faster, so use standard plugs I think about 80-120 baht each and change them every time you change the oil. Sure you can buy special plugs for 600-800 baht each but... that is 2400 baht for a set.

So you're saying change them every 5-6,000km?

Over a 20,000 km, the expensive plugs would come just a little more at best than the cost of standard one with labor/time costs thrown in, no?

[WarpSpeed]

LPG does run a bit hotter and plugs do wear out faster, so use standard plugs I think about 80-120 baht each and change them every time you change the oil. Sure you can buy special plugs for 600-800 baht each but... that is 2400 baht for a set.

So you're saying change them every 5-6,000km?

Over a 20,000 km, the expensive plugs would come just a little more at best than the cost of standard one with labor/time costs thrown in, no?

Yes, wise man and far less likely to have an issue prematurely..

[VocalNeal]

So you're saying change them every 5-6,000km?

Over a 20,000 km, the expensive plugs would come just a little more at best than the cost of standard one with labor/time costs thrown in, no?

I did the math over 5 years ago when I eventually found some Denso LPG plugs after looking high and low. Now mine get changed about every 10,000 along with the oil (synthetic). It runs fine. Oil comes out clean the same colour as it went in.

Starts first time, every time on LPG, runs fine. Slight popping form the exhaust on overun if the vaporizer needs cleaning. Which is about about every 2 years or about 45,000 k and it gets done separately at the LPG installer, as vehicle dealer doesn't do that.

[blacksuitdandruff]

I did the math over 5 years ago when I eventually found some Denso LPG plugs after looking high and low. Now mine get changed about every 10,000 along with the oil (synthetic). It runs fine. Oil comes out clean the same colour as it went in.

Starts first time, every time on LPG, runs fine. Slight popping form the exhaust on overun if the vaporizer needs cleaning. Which is about about every 2 years or about 45,000 k and it gets done separately at the LPG installer, as vehicle dealer doesn't do that.

What's so special about Denso plugs?

Every 10K km seems a bit too much. How do you plugs look when they get changed? I'm guessing pretty clean.

[VocalNeal]

I did the math over 5 years ago when I eventually found some Denso LPG plugs after looking high and low. Now mine get changed about every 10,000 along with the oil (synthetic). It runs fine. Oil comes out clean the same colour as it went in.

Starts first time, every time on LPG, runs fine. Slight popping form the exhaust on overun if the vaporizer needs cleaning. Which is about about every 2 years or about 45,000 k and it gets done separately at the LPG installer, as vehicle dealer doesn't do that.

What's so special about Denso plugs?

Every 10K km seems a bit too much. How do you plugs look when they get changed? I'm guessing pretty clean.

Denso plugs were the only "LPG" ones I could find at the time, I didn't buy them. Standard plugs changed every 10,000. They are clean but obviously worn. I saw the first set now I don't even look.They are cheap so simply get replaced.

[harrry]

My guess is they just have to have the gap set. If the "trained salesman mechanics" do not know how to do this or do not want to they sell you new plugs.

[blacksuitdandruff]

My guess is they just have to have the gap set. If the "trained salesman mechanics" do not know how to do this or do not want to they sell you new plugs.

Is there a specific gap that the plugs need to be for efficient LPG combustion?

[harrry]

To be honest I do not know. I am not a mechanic however my guess is that by reading the colour and deposit of the plug you take out you can easily see if it is correct. There are many colour charts on the net that should help you to tell whether the points are too wide or narrow.

I await the replies of the racing duo that frequent these pages.

[VocalNeal]

LPG is harder to ignite than petrol so the voltage in the ignition system is higher which may lead to premature insulation failure etc.

There is lots of info out there for anyone really interested in looking. Including on NGK's website.

NGK says use one plug colder and set the gap 0.1 mm less. As most of the vehicles serviced where I take mine are LPG this is done as a matter of course. But we still use normal or standard plugs.

This is not rocket science and one does not need "special" LPG plugs at 2500-3000 a set.

[blacksuitdandruff]

LPG is harder to ignite than petrol so the voltage in the ignition system is higher which may lead to premature insulation failure etc.

There is lots of info out there for anyone really interested in looking. Including on NGK's website.

NGK says use one plug colder and set the gap 0.1 mm less. As most of the vehicles serviced where I take mine are LPG this is done as a matter of course. But we still use normal or standard plugs.

This is not rocket science and one does not need "special" LPG plugs at 2500-3000 a set.

Thanks for the words.

So to clarify, you're using standard copper (non-platinum, non-iridium) plugs with a 1 mm reduction of the gaps, right?

[VocalNeal]

So to clarify, you're using standard copper (non-platinum, non-iridium) plugs with a 1 mm reduction of the gaps, right?

Yes. But it is 0.1mm reduction from 0.4 to 0.3 as an example but depends on your car. Don't know what plugs your car uses but I just checked my vehicle manual , mine uses Denso K20PR-U or NGK BKR6E. On the UK website I checked they are GBP 1.86 each which would be 90 Baht ++ so they cannot be anything special not Iridium or whatever. For LPG NGK recommends one grade "colder" so in my case that would be a BKR7E or equivalent.

Again using cheaper plugs and changing more often is mentioned here.

[blacksuitdandruff]

So to clarify, you're using standard copper (non-platinum, non-iridium) plugs with a 1 mm reduction of the gaps, right?

Yes. But it is 0.1mm reduction from 0.4 to 0.3 as an example but depends on your car. Don't know what plugs your car uses but I just checked my vehicle manual , mine uses Denso K20PR-U or NGK BKR6E. On the UK website I checked they are GBP 1.86 each which would be 90 Baht ++ so they cannot be anything special not Iridium or whatever. For LPG NGK recommends one grade "colder" so in my case that would be a BKR7E or equivalent.

Again using cheaper plugs and changing more often is mentioned here.

Are you purchasing your plugs in the UK and having them shipped to you or here in Thailand?

Can't seem to find many spark plugs other than NGKs and Boschs.

[transam]

NGK are the best plugs by far, no question. I have dealt with super charged and Nitrous Oxide powered rides in drag and street racing for years. Tried them all, failures on all except NGK. As Warpy says your eye tells all but for the non tech guy l recommend NGK. If you feel a miss fire, change them and/or fool around with gap or reach of plug. Reach is to do with an extended tip or not. I used extended on the street but normal with nitrous.

[WarpSpeed]

^ I wouldn't argue NGK platinum or Iridium over Bosch but not just plain plugs I just think they're a rare bird to find in Thailand. BTW my mention of color was also in response to the OP mentioning he had checked the color already and his description of the color seemed accurate so clearly he understands that aspect..

The problem with using plain plugs and under-gapping them is a conflict with regular benzine and damaging detonation when running on that fuel.