Can putting 10w30 synthetic oil instead of 5w30

Diahatsu recommends 5W30 SAE or 10W30 either semi-or fully synthetic. Fully synthetic is better oil. Whether you choose 5W30 or 10W/30 depends on your climate. If you have frequent days before zero C, 32 degrees Fahrenheit, you may opt for the 5W30; otherwise, the 10W30 in the one you'll want. Selenia oil tends to be the least expensive of the synthetics and it's a fine oil. (I buy mine at Carefour Suermarket.) FUCHS is also very good and doesn't dent your pocket book. Mobil 1 and Vavoline are quite expensive in Europe, and Motul and ENEOS are outrageous.

5W-30 is a lighter oil, and although is easier for the engine to push through the oil passages (increasing efficiency). If you were running 10W30 or 10W40, there should not be a reason to change. Also...an interesting phenomena noted when drivers switch to a synthetic, many have stated an increase in valve noise. The oil companies denounce their oil causes increased noise, however the fact that there are many before you that have run into a similar issue cannot be ignored. Since synthetic is lighter and designed to flow/stick like conventional, going to a lighter weight in your case was an oops. Go back to a 10W30 and the noise should go back down a little. If you put in a weight of oil that is significantly higher than the design specifications, your fuel economy will go down (not much for each trip, but collectively it will add up) since the engine is working harder to move the oil.

5w30 if you're in a below-freezing climate, 10w30 if not. Synthetic if you can afford it. Change the filter too!

The engine on a 1996 Saturn SL uses SAE 5w-30 engine oil. The recommended oil-change interval for this engine is every 3,000 miles or three months, whichever comes sooner.
---------------- This will help.Thanks.Helpmech.

It might be time to move to 10W30 oil in your 11 year old vehicle. Do you change your own oil? Try 3 qts 5W30 and 2 qts 10W30 of what you normally use.

Get a drain container to fit under car that will hold more than 4litres of oil.
Drain hole is under front of car on bottom of engine on oil pan. 
Remove plug,  allow to drain, inspect the brass washer and file smooth both sides if necessary or sand it, if a plastic washer inspect and replace if necessary.  Be careful not to strip nut upon replacing. Don't overtighten, but a bit more than snug!

5w30 oil typically for all overhead cam engines newer than 1992

Do not mix different oils, eg: 5w30 and 10w30.
Do not use synthetic if not a fresh rebuild or not currently used.

** Slick 50 is an oil additive that puts a teflon coating on your engine parts and I swear by it.
Do not overfill engine - put 3 litres in and allow to run down and check dipstick.
When replacing oil filter be sure rubber seal doesn't stay on engine block.  Fill new filter half-full with new oil and put oil on rubber seal and clean surface of engine where oil goes in.
After filling engine, start and look for leaks.  If you cleaned everything you will notice leak easily.
Shouldn't be a problem unless you messed up seal on filter by not following these directions.
Check with your manual for proper type of oil but should be 5w30.
Good luck.

Depending on your climate. 5W30 is recommended for cold winters. 10W30 will do in a warmer climate. Both oils have the same viscosity when the engine is up to running temperature - that's what the number 30 refers to. The difference is when the engine is cold, the 5W30 is thinner and will flow and lubricate better. The numbers 5 and 10 refer to the viscosity at 0 degrees C.

Be sure to change the filter every time you change the oil. Check the oil level frequently.

You can use any of the following weights of motor oil: 5W30, 10W30, or 10W40. Personally, I use Mobil1 Synthetic 5W30 in my pickup. Synthetic is better for your motor (you can go 5,000 miles between oil changes with synthetic oils) but once you start using it it's better if you stay with it meaning every oil change you use synthetic oil.

They say you can, but remember, not a good idea to switch back if you change your mind later. Personally I'd go with 5w30 for winter then maybe 10w30 or 10w40 for summer. All kinds of arguments for and against synthetic, vs standard. personally I prefer standard & change at proper intervals.

Nope, it's not a problem. The numbers relate to the viscosity or slippery'ness (if thats a word) of the oil. The first number (5 or 10) is the viscosity of the oil when you first start the car. 5 is more slippery than 10. The second number (30) is the operating viscosity of the oil after your car has warmed up.
Simply put, in the winter your oil thickens when it cools down so you need smoother oil (5w30) when you start the car.
Winter = 5w30
Summer = 10w30
Hope this helps.