Howatharra

As a level 2 I get a lot of enquiries about Jab engine issues. Recently the lube oil issue seems to be a common one, possibly arising from a forum at Natfly. I have to stick to Jabiru's recommendations as an L2 and not make recommendations outside of that. However I am currently monitoring four Jab owners who have made the decision to change engine oil types. All four had experienced loss of compression after only 100 to 150 hours on new enines running the normal aviation oil. I inspected the engines after they had pulled the cylinders and found that all four engines had been fitted with what appeared to be chrome rings which had galled with the ring metal forming a fine razor sharp feather pulled upwards running between the piston and the cylinder. The ring gaps on the top ring measured in excess of 5mm in some cases which was surprising in view of the low hours. Three of the engines were 2200 and one 3300. I know the owners and they are good with their maintenance and operation. I recommended that they clean the piston grooves carefully, have the bores lightly honed and checked for out of round, and re-fit using cast iron replacement rings, which all did. So far so good, all four are reporting good results and all are running the Penrite HPR 15/60 synthetic multigrade oil on Mogas. I don't know where they got that particular recommendation from. I'll be watching with a degree of interest to see how it works out long term. The longest hours run since is approaching 40. Howatharra

I've owned four Jab motors, three 2200 and a 3300. All of them were stiff when hot and behaved as you described. A friend has a 2200 in an identical aircraft but his doesn't behave that way. He used a rebuilt engine which had the old barrels re-honed which may explain the difference, i.e. more clearance for the pistons. However he uses far more oil than I do if he runs the 15W50 Shell. Recently he tried out HPR 15w60 oil and now has very little oil burn running RON 95 fuel and has picked up around 100 extra rpm on takeoff. Howatharra.

I was a late starter in the aviation scene but I have made up for that with some pretty intensive activity. I've owned some seven different recreational aircraft, currently got four in the collection, and built up over 2000 hours over the last few years. Built a J250, restored a Slepcev Storch, rebuilt an X Air, currently assembling an FK9 and flying an FK with a Smart engine. This aeroplane stuff is like a disease, once you catch it there is no cure.