An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as a turbo, supercharger, increase compression, timing changes, use of alternate racing fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature and may necessitate a colder plug. A rule of thumb is, one heat range colder per modification or one heat range colder for every 75–100hp you increase. In identical spark plug types, the difference from one full heat range to the next is the ability to remove 70 degrees C to 100 degrees C from the combustion chamber!

A copper core in the ground electrode of every LPG Laserline spark plug improves the temperature discharge, which helps to regulate the higher temperatures in gas-powered engines. A specially developed insulator protects these spark plugs from fouling when being used on regular petrol. NGK Iridium 8 (BKR8EIX) - Two steps colder (Run for 7k on Revo Stg 2+ under duress, removed due to stuttering idle and strong smell of unburned fuel and carbonation on rear of car) Logan Petrol Saloon 1.6 16V (LS09, LS0L, LS0M, LS0P, LS0V, LS18, LS1S, LS1V,... 1598cc 77KW 105HP K4M 690;K4M 694;K4M 696;K4M 697;K4M 698 Logan Petrol Saloon 1.6 (LS0L, LS09, LS0V, LS0P, LS18, LS1S, LS1V, LS1Y,... 1598cc 77KW 105HP K4M 690;K4M 694;K4M 696;K4M 697;K4M 698 NGK BKR6EIX Iridium Spark Plugs offer an enhanced spark over the standard items, and are a 'cooler' running plug than standard plugs on 2.0 Turbo Z20LEx models.Do we need to be saved from our own stupidity or are there sound economic reasons to be so meekly 'managed' by manufacturers? Bosch platinum single electrode - OEM plug supplied from factory (In for 11k on Revo Stg1 - removed due to stutter at 5,000rpm) Yes, in the past I've dutifully observed the recommendations about not questioning the fact that every plug has been specifically set up for my own personal needs BUT out of curiosity I actually 'interfered' by rolling my sleeves up and measured the spark gap variation on my last two N18 MCS. BERU Ultra The brand name spark plug in uncompromising OEM quality! Al well-known international car manufacturers use Beru spark plugs and glow plugs in their vehicles. To retain this high quality level when servicing and repairing gasoline engines, we re Designed specifically for the performance enthusiast Iridium IX offers extreme ignitability, improved throttle response and superior anti fouling.

I know that there are other choices than NGK however I do not have the correct part numbers / advantages / disadvantages again anyone else have more info ?Z14XE, Z16XE, Z16LET, Z16LER, Z18XE, Z20LET, Z20LEL, Z20LER, Z20LEH, X20XEV, C20XE, C20LET, X25XE, Y26SE, X30XE, Y32SE. Been looking into spark plugs for my Mini Cooper S and thought it would be of value to document what I have found out. If you know more or have something to add please feel free to do so. Maybe this thread could become a FAQ ? A special alloy coating covers the shell of every LPG Laserline spark plug, protecting it from the higher temperatures and the increased risk of corrosion. No other manufacturer currently offers a similar coating. NGK Iridium 7 (BKR7EIX) - One steps colder (In car for 6k on Revo Stage 2, changed for 2+, no issues other than electrode discolouration causing concern)