Question About 05 Corolla Taking 5W-20

They did it in anticipation of the tightening CAFE requirements. It was part of a TSB (EG018-06) that came out in 2006-2007. There was a follow-up on that TSB that said it could be used for other models as well. Started with only the 2006-2007 model years, and I'm pretty sure it was extended to all models that used that same family of engines.

5w-20 recommended for these engine families:

AZ, GR, JZ, MZ, NZ, RZ, UZ, VZ series, 1ZZ–FE and 2TR–FE

0w-20 recommended for these vehicles starting in the 2006 model year:

2AZ–FE Camry, 2AZ–FE Solara, 2AZ–FE Highlander, and 2AZ–FE RAV4

Thinner oil is generally better for tighter tolerances - gets into those tighter places more readily. Lower drag on parts means less overall friction, less heat generation - ultimately means you'll see better MPG. But the disadvantage is film strength - on some engines, especially ones with a lot of miles or ones that tend to consume some motor oil. Oil consumption, smoking on startup, and excessive engine noise can start with the thinner oil.

Personally - I've favored a little more film strength than ultimate MPG, so been running a 0w-30 on my newer cars. Plenty of film strength, don't see much of a drop in overall MPG (~ less than 5%), and engines are quieter at idle than the recommended fill of 5w-20. Good all around protection, good low temp flow, additive package is plenty stout, and VI improvers are "supposed" to be better here than in the 5w-30 version of the oil. Also 20 weight oils can also be harder to find - tend to be more expensive than other oils. With 0w-30 and 5w-30, you can find them pretty much anywhere.

I've pulled some UOAs and wear levels are very low with this grade of oil. Also pretty cheap at Walmart - I can get 5 quart jugs of Mobil 1 0W-30 for about $23-$25. Already have a block of Denso "tall" filters - 10K mile oil change intervals seems to be well within the safe range for my driving style.

You have a 1ZZ-FE - don't worry about the other series of engines. That TSB just covers many of the newer Toyota engines - AZ is one of the more popular "corporate" engines out there. Think Camry, Highlander, Rav4, etc.

The 5w-20 is actually considered a thinner oil than the 0w-30. 0w-30 is only thinner on very cold startups (subzero temps). Remember these are SAE multigrade oils - hence the two oil weight numbers. First number is the oil weight in winter (hence the "w" designation), second number is what the oil weight when hot (graded at 100 degrees C).

At operating temperatures - the car cannot tell the different between the 0w-30 or 5w-30 motor oil weight, as they both spec at a 30 weight oil when hot. Unless the car is started up at subzero temps, can't tell much from a 5w or a 0w weight oil.

I like the 0w-30 grade as they seem to do the best job for my car. As mentioned in another post - pick the oil that works best in "your" car. A 0w-30 oil might be inappropriate for your driving conditions - might not get that cold - that case, you'd get good results with a 5w-30, definitely be easier to source and find in most stores. Some cars like thinner oil - some like thicker oils. One car might shear down a 0w-30 faster than a 5w-30 oil, due to the increase in viscosity index improvers - another might prefer the 0w.

Best way is to experiment with different brands and grades - see what works best in your car. Conventional, synthetic, blends? Up to you on what to run, can't really advise you other than to put out information. Up to you to go that final step and try these oils out.

The new dipstick on the 9th gens gives you about 1/2 quart more oil in the sump. Still plenty of space left without overfilling the crank case. You don't need to install the new dipstick - just note the height of the oil fill level on the current dipstick you have (new level is about 1/2" higher than the old dipstick marking). Some got the new part installed free from certain dealerships for customer appreciation. Others just purchased it separately just to have.

To give some owners a little more capacity, little more oil. Even a small increase in oil capacity can have a dramatic effect. More oil = more reserve capacity to stay cooler, more additives to fight corrosion and combustion byproducts, give you a buffer to hedge against oil consumption especially with lower viscosity oils like 5w-20. If you read up on make up oil - you'll see that a small amount of fresh oil added can make a huge impact on overall oil longevity.

But that has to be approached smartly - as the sumps in the cars are not huge, can be easy to overfill, especially at a service station (oil gun fill). If doing this as a DIY - little easier to control how much oil you can put in. Half a quart extra doesn't hurt these 1ZZ-FE - most of the time, owners will overfill that amount and not know it. I know when I change my oil - I'll just dump in all 4 quarts of oil, there will always be some oil inside the engine + I pre-fill the oil filter with some left over oil from previous changes. Works out to almost exact 4.5 quarts in my sump.