Oil Mixing help

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I need to do an oil change on my car & it does burn oil sometimes (especially at weird times). A friend I have that is car knowledgeable says to use thicker oil & I do put 10w30 in the summer. But, being on the cheap with the price of oil through the roof these days, I only have 3 bottles of Shell dino 10w30 left. So, I wanted to know your opinions if I can do this combo of 3 x 1L 10w30, 1 x 1L 5w30 & the rest (about .7L) of Motomaster 15w40 Diesel oil? Now, I have been topping up with the diesel oil & haven't had any problems, but one of my friends told me that diesel has some additives that may be diesel specific, thus the reasons I'm asking. Oh, & I'm just waiting for Costco to put the Shell oil on sale then I'll buy 2 cases. I bought more 5w30, but I used my last stock of XD-3 for this past oil change from January.
 
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Most but not all diesel oil is both diesel and gas rated. You need to check on that. But diesel oil does not have any additives that are bad for gas engines, even if its not gas rated. No matter what less than 1 QT of diesel oil in the mix will not hurt anything. Thicker oil may or may not solve the problem. How is the oil pressure. Does it smoke? Only at startup or all the time? Compression test? If the compression was low you could try Kreen or Auto-Rx that would (might) clean the ring areas so the rings would seal better. Or you could have an engine built by a new guy on the job where he lined up all the ring gaps perfectly on his first day.
 
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EloManga

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Ok, sorry, the engine is a 2.5L V6 Mazda KL-ZE (J-spec). I swapped it into my Probe GT in 03'. It doesn't smoke on startup or anything. The compression is unknown. The guage doesn't work properly so...? It does pull hard though if I punch it. I am doing alot of highway driving right now. When it does smoke, it's usually on a down shift from 5th to 4th. Or, if I step on it a bit, the pedal gets really hard, like I can't go light on the throttle, I have to go a bit more & I've noticed then that it smokes, but not all the time. In the current oil, I put Seafoam, which didn't really do anything, but I will put it again as I still have some. Oh, I did run Auto-Rx before, didn't do anything.
 
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Wait, so you drive around with a broken throttle body and you're worried about mixing 5w30 and 10w30?
 
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Originally Posted By: yonyon
Wait, so you drive around with a broken throttle body and you're worried about mixing 5w30 and 10w30?
Wait, your guess may be "spot on" but, where does the OP say that(broken TB)? Sounds go me like the throttle linkage is binding and there is a bit of carbon in the engine the is burned off when the tranny downshifts @ WOT and the smoke comes out of the exhaust! From the little bit that the OP wrote, it could be a number of things. Mixing the oils aren't an issue but, it does seem that there is some fine tuning to be done in the throttle or TB area where the OP "MAY" discover a TB issue but, we don't know that yet! We don't even know yet what color the smoke is that the OP is mentioning apon tranny downshift. Sounds to me like there is a bit of a head gasket or plenum issue also. I could be entierly off here!
 
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I basically have the same engine. My personal opinion is mixing oils at top-off is fine, but I try not to mix in an OC. That engine can use everything from 5W-20 to 10W-40 (if driven consistently over in temps of 100F) according to Ford. I've had good luck with mine although it uses about a quart every four or five thousand miles. I've run both synthetic and blend high mileage oils and syn like QSUD stockpiled from rebates. I'm probably going with 10W-30 next oil change...
 
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Originally Posted By: Char Baby
Originally Posted By: yonyon
Wait, so you drive around with a broken throttle body and you're worried about mixing 5w30 and 10w30?
Wait, your guess may be "spot on" but, where does the OP say that(broken TB)?
Sorry about that, I meant to try and point out that an improperly function throttle that could get the OP stuck in a tree or a lake or something could be a bigger problem than an other-than-ideal oil choice.
Originally Posted By: Char Baby
From the little bit that the OP wrote, it could be a number of things. Mixing the oils aren't an issue but, it does seem that there is some fine tuning to be done in the throttle or TB area where the OP "MAY" discover a TB issue but, we don't know that yet! We don't even know yet what color the smoke is that the OP is mentioning apon tranny downshift. Sounds to me like there is a bit of a head gasket or plenum issue also. I could be entierly off here!
The "broken throttle body" was meant to be a wild guess that represents the symptom described and the possible dangers. If I were going to make a guess and bet a nickel on it I'd go with throttle cable kinked during engine install. That and a filthy throttle body are both likely suspects that are easy to look for.
 
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[Quote: yonyon]The "broken throttle body" was meant to be a wild guess that represents the symptom described and the possible dangers. If I were going to make a guess and bet a nickel on it I'd go with throttle cable kinked during engine install. That and a filthy throttle body are both likely suspects that are easy to look for.[Quote] Exactly! But also, if I had to take a guess on what color the smoke was(apon WOT downshift), I'd say it was black due to dirty combustion chambers. Just another guess w/o knowing more!
 

EloManga

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Sorry guys, I didn't realise what site I was on. You guys actually want all the details & respond accordingly. The colour of the smoke that comes out on downshift is blue. Is my tb binding? I don't think so. I did want to lube it, but I've been very busy & had no time. I don't put the pedal on the floor when this happens (the stickyness), but I should look into it. I drive normally most of the time, so it's not a big issue. My issue is the oil & the mixing of oils without having any problems. I once put some of the same 15w40 in a lawnmower & it killed it once it ran for over 5 mins. It too burned oil & I tried some thicker oil to see & it lost all it's power. That's one reason why I'm asking here if doing so would have the same effect on my car engine. As for why it burns, these engines have a problem with valve seals or retainers, I forget exactly, but it's one of those. I'm not in a position to get the work done at the moment either.
 
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OK! Yes, you can mix oils with confidence! A little or all 15W40 won't hurt a thing in your engine although it's a little thick. I can't answer as to why the 15W40 killed your lawnmower! Lot's of folks use 15W40 in their mower. If there is blue/black exhaust smoke apon a cold startup, it's most likely valve seals. If there is that same smoke while driving, it's oil getting past the piston rings If ther is that same smoke druing wide open throttle(WOT) or even harder throttle input, most likely it's carbon deposit atop the pistons. But the engine needs a bit of attention! Maybe, not even alot! Some complete fuel system cleaner may be in order. GUMOUT Regane, Cheveon Techron or some of the other popular Fuel System Cleaners(FSC) would be a good idea, along with a throttle body(TB) cleaning would also be good places to start. Lots of things to be checked, one at a time such as the plugs/cylinders to see if there is oil present.
 
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EDIT timeout! And to add: A High Mileage Motor Oil such as Valvoline MaxLife or Quaker State DEFY, Pennzoil HM and others, may also help due to their specific additives.
 

EloManga

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Thanks Char Baby, yes, I don't know why the 15w40 killed the lawnmower since you use a w30 oil in it anyway? As for my car, there is no smoke on wot or anything, it's just if I downshift & go lightly on the throttle afterwards it'll smoke, sometimes & for a bit, like 2-3 seconds, then stop & act as if nothing happened. I have cleaned the TB, recently too. I use 94 octane all the time, there is no smoke at startup, I've used seafoam in the engine, I guess I could add some to my next tank as well? Believe me, I take care of my engine, it's just how these engines are.
 
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Your welcome and I too have had engines that were known for their particular issues. That's too bad too because they're a nice V6 engine!
 
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Do a compression test with and without oil in the cylinders to rule out the oil rings. Friend had a Volvo that smoked just as described, after going down hills in gear. High vacuum sucking oil past the bad valve stem seals, replacing them fixed the issue.
 

EloManga

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Well I've had absolutely no time in the last few months, so hopefully I'll find some time & be able to do one. The vacuum sucking oil theory does sound believable as it is strange when oil smoke is present as it's not done on wot or startup. Slight off topic question, is it bad to mix dino oil into synth. oil?
 
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