As posted above, mixing 5w30 with 10w40 will give you an oil that performs somewhat better in the cold than 10w40, but less good cold than 5w30, and that has a viscosity a bit higher than 5w30 but a bit lower than 10w40.Similarly, you may ask, is it OK to put 10w40 in a 5w30?
The recommended oil viscosity for your vehicle, according to Kia documentation, is 10W-40. If you drive the vehicle in exceptionally cold weather, well below 32 degrees, you can use 5W-30 oil but even 10W-40 is still perfectly OK to use if outdoor temperatures are below freezing.
Likewise, is it bad to mix 5w30 with 5w40? Mixing different oils will not improve the performance or efficiency of the engine in any way. The additives in synthetic oil may have limited or no effect at all when mixed with a regular engine oil. You can use 1 litre of 5W30 mixed with 5W40 and it will not cause any sort of ill effects to the engine.
Similarly, you may ask, which oil is better 5w30 or 10w40?
5w30 is a motor oil which is synthetic and has a viscosity of 5 when in low temperature and 30 when in high temperature which is normally at 100 degrees celsius. 5w30 is less viscous while 10w40 is more viscous. The 5w30 has a viscosity of 30 at high temperature while a 10w40 has a 40 viscosity at high temperatures.
Can I use 10w40?
Of course you can use it. But it may lower your gas mileage by 1-2%, will vary with car, and this loss may only be temporary. My car also calls for 5W30 or 10W30. I had some 10W40 Valvoline that I used in an oil change.
Is Thicker oil better for high mileage cars?
A: Yes. This is a practical method to improve oil pressure in an older, high-mileage engine. The slightly thicker oil film from the heavier base weight oil — 10W — can help protect worn engine bearings as well. The engine does not leak and I've never seen a whiff of blue smoke.What happens if you put the wrong oil in car?
Motor oil slip-ups. The brand of motor oil matters little, but its viscosity grade (10W-30, for example) is important. Use only what the owner's manual specifies. Using the wrong oil can lead to reduced lubrication and shorter engine life. If the manual says to use synthetic oil, do so.Is it OK to use synthetic oil in high mileage cars?
It's not accurate to say that you should never use synthetic oil in an older car. In fact, Castrol EDGE High Mileage is a synthetic oil designed specifically for high-mileage cars. If the car has been maintained and is in excellent running condition, the synthetic oil may protect the vehicle and prolong its life.Can I use 15w40 instead of 5w30?
First, the oil viscosity change won't cause your head gaskets to blow off. The real problem with using 15w40 in place of 5w30 is the increase thickness of 15w40. Obviously the heavier oil would be a good thing.Which oil is thicker 5w30 or 5w40?
The number after the 'w' represents the thickness of the oil in normal or warmer temperatures. The 5w40 has a higher viscosity in warmer temperatures than the 5w30.What happens if you put thicker oil in your car?
Oil that's too thick may not flow quickly enough Since thicker oils don't transfer heat as well as thinner oils, operating temperatures will increase, too, possibly leading to accelerated chemical break down and harmful sludge and deposits.What happens if you start a car without oil?
Without oil, the engine runs for around 15 minutes without bursting into a cloud of smoke, but taking it apart reveals some serious damage. If the oil-less engine had run for much longer, it very well could have seized. So, don't drain your car of oil just to see what happens. Unless you want to buy a new engine.Which is thicker 10/40 or 20 50 oil?
The smaller number, (the 20 part of 20w-50) describes how the oil behaves at 40 deg C and a 20w at 40 deg C is about 10 times thicker than your engine wants. A 10w-40 is better at around 6 times thicker and a 0w-40 is much better at about 4 times thicker.Does engine oil get thinner over time?
In case of a petrol engine, if the oil gets thinner it means it is mixing with gasoline, therefore contaminated. Normal use of oil will make it thicker over time. If it gets thinner, you have an issue.Will thicker oil reduce oil consumption?
A lot of oil-burning takes place because an engine's piston rings are worn out, and thicker oil won't fix that. They also count on low-viscosity oils to reduce friction and drag (the work of simply moving the engine parts through thicker oil), which improves mileage.What is 5w30 oil used for?
Uses of 5w30 5w30 is used in light-duty diesel engines, light-duty petrol engines, and automotive gasoline engines. 5w30 engine oil is preferred for engines working in cold climates, as it gives good flow at lower temperatures.How long can oil filter last?
three months
What is 5w 40 oil used for?
5W-40 motor oil The 5W-40 viscosity is a prevalent recommendation for performance engines in European vehicles with gas-powered engines, and in American diesel pickup trucks.Will heavier weight oil stop leaks?
As an engine heats up, the oil thins, becoming more susceptible to leaks through faulty gaskets. Draining the oil from your vehicle and replacing it with a thicker weight or synthetic oil can help to prevent oil from leaking through some of the smaller breaks in the gasket seals.Is 5w30 good for summer?
5w30 is a great multigrade oil for use in low starting temperatures as well as high summer temperatures. It is also more fuel efficient since it creates less drag on the bearings and moving engine parts. 10w30 is thicker and may provide better sealing capability for older engines.Is 10w40 good for summer?
Using 10w30 oil in cold weather will help reduce excessive oil temperatures and drag as the engine warms up. Using 10w40 oil in the summer will help the oil stick to internal components in high temperatures, avoiding the wear and tear from metal-to-metal contact between moving parts.Is synthetic oil thinner than regular oil?
Synthetic engine oil also offers much greater wear protection, and prolongs the life of the engine. Also, synthetic engine oil is much thinner than conventional engine oil. That means it meets less resistance while working it's way through the engine. 
