Jim27 Posted December 21, 2013 Report Share Posted December 21, 2013 Any idea why engine oil would turn red? This was Castrol Edge 5w40 fully synth and was put in by myself (so no garage meddling) a few months (and about 2,000 miles) ago. 2003 BMW 330ci manual running LPG. Recently had a radiator leak so ran on normal unlead for 60 miles until I could replace the rad (now done). Coolant used is blue, not red. Hydraulic fluid level seems fine. When you wipe the dipstick on tissue it looks more of a red-brown colour but there's an undeniable red colour to the oil...? Looks more like ATF than engine oil! Link to comment Share on other sites More sharing options...
mit Posted December 21, 2013 Report Share Posted December 21, 2013 Might be a side effect of the LPG? It should normally go black after a while,, due to exhaust gases from combustion getting into it... Link to comment Share on other sites More sharing options...
bungers Posted December 21, 2013 Report Share Posted December 21, 2013 What colour was the stuff you took out? Link to comment Share on other sites More sharing options...
Jim27 Posted December 21, 2013 Author Report Share Posted December 21, 2013 Stuff I took out was black. I check the oil fairly regularly and it always looks the usual yellowish straw colour when fresh then just darkens slowly with use. It usually takes a lot longer to darken when using LPG though as there's far less crap and muck in the gas than there is in petrol meaning far less dirty by-products from burning to get into the oil. Have done 2 oil changes since buying it and never seen ordinary oil turn red before... Very peculiar! Link to comment Share on other sites More sharing options...
sag2 Posted December 21, 2013 Report Share Posted December 21, 2013 (edited) Just a thought but are you sure it wasn't transmission oil you put in by mistake,as that's red never seen oil go red and I've had a few LPG motors over the years just a thought Edited December 21, 2013 by sag2 Link to comment Share on other sites More sharing options...
Jim27 Posted December 21, 2013 Author Report Share Posted December 21, 2013 Definitely wasn't ATF fluid or similar! Link to comment Share on other sites More sharing options...
Trevor Posted December 21, 2013 Report Share Posted December 21, 2013 First things first. I'd do an oil change before I drove it again. Link to comment Share on other sites More sharing options...
Jim27 Posted December 21, 2013 Author Report Share Posted December 21, 2013 Interesting tech commentary I found on a Porsche forum about oil naturally turning red as it oxidising, although soot from petrol generally darkens the oil and hides this change: "In use, the hydrocarbon molecules that make up the base oils in the engine oil oxidise (react with oxygen from the air). This happens far more at high temperatures and so areas like under the piston crowns or on the piston walls are where a lot of the oxidation of the oil happens. The molecules formed tend to be dark and some of them are red/amber/orange - they are on the way to becoming varnishes. This is why you will sometimes see an amber/orange stain on those areas of a stripped engine. You do not always see this amber/red period on your dipstick. The other contributor to colour change of the engine oil is soot from incomplete combustion of the gasoline. Soot is black and so it often masks the underlying "reddening" of the base oil. Oil formulators add anti oxidants to their engine oils to slow this oxidation process down. The main anti oxidant used in the past was zinc dithiophosphate (ZDDP or ZDTP). Castrol GTX 20W/50 will be far more susceptible to oxidation than Brad Penn Part Synthetic 20W/50. The Brad Penn contains a mix of mineral and synthetic base oils and the synthetics are inherently more resistant to oxidation. Also it contains a heap of ZDDP, added primarily to give wear protection but, as I mentioned, it is also a very effective antioxidant." Link to comment Share on other sites More sharing options...
Jim27 Posted December 21, 2013 Author Report Share Posted December 21, 2013 Just looked again and without light passing THROUGH the oil it certainly looks less red and more brown. This is the dipstick wiped on kitchen towel. ...and this is the oil dripped onto clingfilm (over a white patch of the kitchen towel so we can see the colour properly). I suspected the oil touching the kitchen towel would soak the base oil into it and leave the crap on the towel surface, giving a false colour. You can see from the drils on the clingfilm that it's a little redder but definitely more brown than red when light's shone ON it rather than THROUGH it.... Link to comment Share on other sites More sharing options...
Trevor Posted December 21, 2013 Report Share Posted December 21, 2013 Weird. Panic over.. Link to comment Share on other sites More sharing options...
Rebel Posted December 21, 2013 Report Share Posted December 21, 2013 Car's 'time of the month' perhaps? Phantom Mark, sag2 and mit 3 Link to comment Share on other sites More sharing options...
BmEagle Posted December 21, 2013 Report Share Posted December 21, 2013 Car's 'time of the month' perhaps? Brings new meaning to changing oil periodically ? sag2, Rebel and Phantom Mark 3 Link to comment Share on other sites More sharing options...
Phantom Mark Posted December 22, 2013 Report Share Posted December 22, 2013 Daymn never seen that before ! Link to comment Share on other sites More sharing options...
DJ Syxx Posted December 22, 2013 Report Share Posted December 22, 2013 Car's 'time of the month' perhaps? Hence why cars are referred to as "she" lol Rebel 1 Link to comment Share on other sites More sharing options...
Jim27 Posted December 22, 2013 Author Report Share Posted December 22, 2013 Well there ya go. Apparently all engine oil turns red, however it's usually masked by the amount of soot that gets into the oil from burning petrol or diesel, so the oil darkens from soot contamination before you get to see the red colour change come through. Because my car runs LPG there's far less soot, so there's no soot to mask the colour change of the oil. Allegedly. Personally I think it's been eating people at night and was just finishing digesting them when I checked the oil dipstick... Link to comment Share on other sites More sharing options...
Schumacher Posted December 24, 2013 Report Share Posted December 24, 2013 I use Fuchs Titan Race Pro in my other car and it's red straight from the lab. Link to comment Share on other sites More sharing options...
