what is the difference between 10w30 and 10w40

10w30 is thinner when hot, so it flows easier in cold starts but might not protect as well in high heat. 10w40 gives a bit more film strength at operating temp. For trail riding in 90°F, I'd go 10w40 to reduce wear, especially with valve noise.

Valve noise could be from low oil pressure. 10w40 might help if your clearances are opening up. I switched from 30 to 40 in my 450 and the ticking quieted down. Just don't go heavier than 40 or you'll starve the top end.

Stick with what the manual says. ATV engines are designed for specific viscosities. If it says 10w30, running 40 can cause drag on the oil pump and reduce flow to critical areas. Check your owner's manual first.

I run 10w40 year-round in my utility quad because I tow and ride in mud. Never had issues. The 40 weight handles heat better. If you're hearing noise, it's probably worth trying a change to 40 and see if it helps.

Actually, 10w30 and 10w40 have the same cold viscosity (the 10W part). The difference is only at operating temp. For your temps, 10w40 is fine. But if you ride in cold weather, 10w30 starts better. I use 30 in winter, 40 in summer.

Agree with the summer/winter switch. I do 10w30 from Nov to March, 10w40 the rest. That valve noise might be lash adjustment needed, not oil. Check your valves before blaming the oil weight.

I'm a mechanic. The 10w40 has a higher high-temp viscosity index, meaning it resists thinning more at 212°F. For trail riding with mud and hills, your engine runs hotter. 10w40 is safer. But change it every 50 hours or less.

10w30 is fine for most riding. I've got 500 hours on my 300 using 10w30 synthetic and no issues. The noise could be normal. If you're worried, do an oil pressure test. Don't overthink it.

Partial disagree with the mechanic. 10w40 can be too thick for tight-clearance engines, causing oil starvation at startup. If your manual says 10w30, use it. Modern synthetics already protect well. I use 10w30 synthetic year-round.

I switched from 30 to 40 and my oil consumption dropped. The 40 sealed the rings better. But I also noticed slightly lower RPMs at WOT. Trade-off. For your valve noise, try a thicker oil, but also check the cam chain tensioner.

Don't ignore the noise. Could be a worn cam or rocker. Oil weight won't fix mechanical wear. I'd do a compression test and pull the valve cover. Better safe than rebuilding a top end.

10w30 is what most ATV makers spec because it balances flow and protection. 10w40 is for high-performance or high-mileage engines. Your 200 hours isn't high mileage. I'd stick with 30 and add a zinc additive if you're worried.

I use 10w40 in my Chinese knockoff because the engine runs hot and has loose tolerances. It helped with smoke. But your Japanese quad is better built. Try 10w30 first, then 40 if you still have noise. Cheap test.

Creek crossings mean water can get in. 10w40 might emulsify less than 30. I've seen water in oil from fording. Change oil often if you do deep water. Weight matters less than frequency.

Been riding 20 years. The difference is minimal in modern engines. Just use a quality synthetic 10w30 and change it on schedule. Valve noise is more likely from carbon buildup or clearance. Focus on maintenance, not oil weight.

I run 10w40 in summer because my trails have steep climbs and I ride aggressive. The engine gets hot enough to boil 30 weight. If you're easy on the throttle, 30 is fine. Your call based on riding style.

What brand are you using? Cheap 10w40 can be worse than good 10w30. I use Rotella T6 5w40 actually. It's a diesel oil that works great in ATVs. High zinc and shear stable. Just a thought.

Check your oil pump. If it's worn, thicker oil might not help. I had valve noise from low pressure, and 10w40 made it worse because the pump couldn't push it. Went back to 30 and adjusted the pump clearance.

I asked my dealer and he said 10w30 is recommended for warranty. He said 10w40 can void it if there's a failure. So if you're still under warranty, stick with 30. After that, experiment.

Valve noise is often just normal mechanical clatter. My 400 does it too. I run 10w30 and it's fine. If you're really concerned, do a leakdown test. Oil weight is a band-aid, not a fix for actual problems.