I have 3 TT Pro engines - one .61 and two .46s. The .61 and one of the .46s are about three years old with about 10 years of flying on them. The other .46 is fairly new. Since TT engines don't come with a plug I used what was on hand which happened to be an OS8. All three engines have the first plug I put in them still in them. THey run flawlessly and start with one flip of the cihcklet stick. I don't think any of them has ever dead sticked outside of trying to wean it of fuel.[8D]. I might add I think the TT Pro engine is the absolute best buy on an engine out there. I own Tower, OS, Saito, and TT engines, of these TT Pro is my pick