Can you mix oil?

[Chris41586]

New bonehead here figuring out the trails! Just got a 2008 Suzuki Z400, and the guy said he just did an oil change, but needs a little more because he was letting it cycle through before topping it off. He says he used ATV Power SAE 5W-40 Synthetic 4T Engine Oil, but the manual just says use 10W-40. He lives a couple hours away, where it's a little bit colder, so I'm assuming that's why he used 5W instead of 10W? Anyways, I only need a little bit more oil, and since it's already new in there, can I put the 10W in and let it mix? Also, does the brand being the same matter at all? I haven't gone out and looked in person yet, but actual ATV oil seems a bit expensive compared to just getting some standard oil at AutoZone, and the online manual I found isn't that clear on options. I'd appreciate some feedback and experience in this area, as well as the best place to get oil and filters when it's time. Thanks in advance!

[Mech]

Since it's got synthetic oil in it now, you need to top up with synthetic oil. It doesn't have to be the same brand, but you should try to get an oil with the same rating... Probably SF or SG.

If you want to change to a straight petroleum oil(non-synthetic) you can at the next oil and filter change.

[Chris41586]

What about the 10W part? 

Only reason I'd use that over 5W, is because when I do an oil change, I'm gonna use 10W, and right now I don't need a whole quart, so half of the 5W will never get used

[Mech]

If the 10 grade oil you are thinking of using isn't synthetic, then you shouldn't mix it with the synthetic oil that's in your motor.

Perhaps it would be easier, and give peace of mind, to do an oil and filter change right now. Then you can put regular petroleum 10w30  in it and have some to top up in future. Petroleum oil's about half the price of synthetic. If you have to buy much synthetic(due to packaging practices) to do the top up, it won't cost much more to buy a pack of petroleum and do a change.

[Chris41586]

The only 5W-40 they had was $18 a quart!😒 You're right, at that price I can just put new oil, but don't I have to use only synthetic from now on since that's what was in there? If so, that's a bummer, because it's twice the cost. Hopefully I can go longer in between changes then

[ShaneM]

Does The z400 use separate oil for gearbox & engine oil?

[Chris41586]

Not that I know of. The guy at the store today was saying the "4T" oil is for bikes with a wet clutch, and whatever else it lubricates, and that's why you use that instead of regular oil

[Mech]

If you look in the workshop manual it says to use regular old petroleum oil. A lot of the more modern oils, whether synthetic or petroleum, have additives in them that aren't really doing anything useful in a motorbike engine, and which could even be doing harm. I stick with petroleum oil in my bikes, and of the spec they stipulate.

[Chris41586]

That's what I want to do, because synthetic is also quite a bit more expensive, but can I still do that AFTER he's used synthetic? Of course I want to go back to regular

[Mech]

Yeah you can change back to petroleum oil. No worries. It's done all the time.

Get the motor hot, drain the oil, change the oil filter, and then put in your new oil. The tiny amount that sits in the cam box and oil galleries etc is not enough to cause a problem.

[Chris41586]

Cool, thanks Mech. Definitely makes me feel a little better after having to drop so much money at one time, between the bike and safety gear (just a helmet, gloves, and goggles for now). Ready to ride this weekend!

[Mech]

No trouble Chris.. Have fun...  but don't get caught !

[Nadamamasboy]

I know there are numerous synthetic blends,  which means they aren't pure synthetic.  You could probably top off with regular oil but this will make your oil thicker when cold. 

[brad_h1]

You shouldn’t have any problems at all. 

[Matman]

How low is the oil that needs to be topped off? There is a min/max to all oils. I'd highly recommend just replacing your oil and filter. 

[olddude]

Mixing two weights isn't a real problem but if you have pure synthetic oil in there it's not a good idea to mix in carbon based oil. There is however a synthetic blend oil that you could possibly mix without problems between changes. Oil is oil and some oil is a far cry better than no oil.