SeattleGS400

iTrader: (1)

I was previously using Mobil1 10W-30 in my car (grabbed the wrong case back then!), and recently switch it over to Mobil1 5W-30. One thing I noticed, but I can't solidly verify just yet until I get more mileage on using 5W-30, but it seems like I'm getting about 5-10% better gas mileage on 5W-30 than on 10W-30 (based on 3 tankfuls of driving). Could this be due to that 5W-30 is a lighter oil than the 10W-30?

I know that the labels on the quart bottles of the above Mobil1 oils are similar with one exception, the 5W-30 has this extra line on it:

"Mobil1 5W-30 provides superior fuel economy compared to conventional SAE 10W-30 grades."

I didn't think I'd see this sort of increase in fuel economy (5-10% increase) using 5W-30 over 10W-30. The only compouding factor could be that I also did a simple drain and refill with my ATF when I changed my oil.

Can anyone also share experiences with using 5W-30 vs. 10W-30 in their cars, with respect to fuel economy?

Lexmexico

You can read most of my other posts regarding different grades.

I have experimented here at a 7,700 foot altitude with Mobil 1 5W-30, 10W-30, and 15W-50 (which i am currently using). The 5W-30 and 10W-30 felt great, but boy oh boy did they burn oil in this hill environment. I did get slightly better MPG, but I was changing the oil more often maybe 2000-2500 miles (with filter change each time). The 15W-50 does not flow as well, but it does not burn one bit, and it is much easier to go up hills and hit high speed (feels like a truck), but gives me piece of mind. The only difference between the 5W-30 and the 10W-30 is the 5W-30 flows faster through the system. One downside (but you will likey never experience it like I have) is oil shearing from hard use. The 15W-50 does not burn (or I like the use the word cut down) from 50 weight to lower, because it is already a high weight. However, my use of 30 weights led me to believe I was running down a road of trouble here. However, in the States I have never experienced a problem with 5W-30.

hyperopt

Both 5-30w & 10-30w behave like 30w at normal operating temperature which is the predominating temp for running engine. I did not observe any change in gas mileage with the two oil weight. I found that tire pressure and driving habits are significant contributors to gas mileage.

Lexmexico

Another thing besides tire pressure, having good alignment, balance and doing rotation. I do alignment every month because of where I live (and it is usually a good thing) and balance and rotation every 6,000 miles. Cleaning out your air filter for your engine, and a dose of Techron fuel injector cleaner. I personally find that putting the Techron in and leaving it in the gas tank over night (after doing a full fill up) does a much better job than putting it in when you are about to fill up.

kreativ

Any reason why the instructions for these type of products always state to pour it in when the gas tank is almost empty?

I purchased a few bottles of Chevron Fuel Injector Cleaner with Techron. Then I noticed there's also a Chevron Techron concentrate on sale, much more expensive.

Lexmexico

I have no idea. In fact, every mechanic here who has used that product or another product called Restore, the injection cleaner not the oil additive, gave me precisely the same instructions. I have tried following the instructions on the can, but felt nothing different afterwards. Only when I heeded the mechanics' advice did I start to feel like the engine ran smoother.

I also felt, though I cannot confirm without further in-depth analysis, that Techron seems to also loosen up the sludge that gradually accumulates in the gas tank. Whatever it was passed easily through the engine, and car feels much smoother when closer to empty.

SeattleGS400

iTrader: (1)

I think it's just a matter of mixing. Think about this: you want to add some additive (say sugar) to a glass container. Do you add the sugar last or do you add it first? If you add it first to an empty glass container, then add water, it will mix faster and more uniformly than the other way.

Lexmexico

Sorry, I misread your answer originally,

True, that makes sense. The only thing I would add and this comes from my mechanic is if you are going to do this with a near empty tank, to put this in at the gas station not before. Too much Techron per part of gasoline and make the glue on the injectors come undone. Lexus reassures me this would not happen, but I have heard of this happening in other vehicles.

What I do is pour the stuff in to my full tank when I get home, then leave the car sit overnight. I find the Techron works much better this way.

JCtx

The reason for putting it when the tank is empty is simple: it should be mixed with FRESH FUEL. Same thing with fuel stabilizer. You can fill up your tank and put the techron or stabilizer at home; no problemo. But in the case of fuel stabilizer, make sure to drive the vehicle at least 5 miles after treating the fuel, so the entire fuel system is properly protected.

Hope this helps.

JC

SeattleGS400

iTrader: (1)

I finally did some more driving, and here's what I've come up with with respect to the 5W-30 vs. 10W-30 fuel economy debate:

Using 5W-30 Mobil1 synthetic oil nets 10% better city fuel economy vs. 10W-30 Mobil1 synthetic oil during my informal short-city trip driving study.

Driving methodology: Drive for 3,600 miles on 10W-30 Mobil1, then switch over to 5w-30 Mobil1 (driven for 4,100 miles). Most trips were short (<5 miles) around town, so the car doesn't get fully warmed up for about 50% of each drive segment (i.e. if my trip is 4 miles long, the car does not fully warm up until about 2 miles into the trip). No freeway trips were recorded as they were different distance freeway trips on each oil viscosity (could skew the overall results, esp. if I drove on long 600 mile drives). Same tires used and properly inflated. Chevron supreme gas used 90% of the time. Upon fill-up, recorded amount of gas filled and miles driven on gas receipt, then reset odometer.

10W-30 Mobil1Stats
time period driven: Oct 03 to Jan 04
oil consumption: no oil was consumed, and no extra oil was added
short city miles driven: 1786.00
gallons used: 106.76
Avg. MPG: 16.73

5W-30 Mobil 1 Stats (FYI, this is the Lexus recommended oil viscosity)
time period driven: Jan 04 to March 04
oil consumption: no oil was consumed, and no extra oil was added
short city miles driven: 2432.50
gallons used: 137.78
Avg. MPG: 17.65

Possible confounding factors:

a. OEM Iridium sparkplugs replaced near the end of the 10W-30 Mobil1 run with new Denso Iridium plugs(about 300 miles were driven on new plugs). The original OEM plugs had 20k miles on them (based on dealer records later found on them), so this should be negate any effects of putting in new plugs.
b. Chevron fuel injector cleaner used at end of 5W-30 Mobil1 run (about 300 miles were driven with and after the fuel injector treatment).

Analysis: According to to Mobil1, "Mobil1 5W-30 provides superior fuel economy compared to conventional SAE 10W-30 grades." Although I used both synthetic oils (Mobil1) in this comparison, the lighter weight 5W-30 Mobil1 gets 10% better gas mileage than the 10W-30 Mobil1. The driving conditions were similar and everything was pretty much held equal. If you drive short distances in the city as I do (< 5 miles/trip), the engine oil does not spend a good amount of time at the normal operating temperature (esp. during the fall-winter months), therefore, it has on average a lower viscosity than 10W-30 oil when not fully warmed up. If I was driving at full operating temperature, the 2 oils would have the same viscosity (as it states on the Mobil1 website), and the fuel economy would be more similar.

Summarily, the above short-trip observations nets the following: if you drive in city conditions on short hops (< 5 miles/trip), using 5W-30 Mobil1 will net a 10% increase in fuel economy over using 10W-30 Mobil1. Unless your car needs the higher viscosity (high-gain engine mods or if your car burns a little oil), stick with the lower viscosity 5W-30 to net maximal fuel efficiency.

On a side note, I wonder how using 0W-30 would affect the fuel economy vs. 5W-30. . .

Lexmexico

I would not use that 0W-30 unless you are in a really, really cold place. While the 30 weight is fine, that 0 will flow 7 times faster than water according to Mobil, and it will leak. However, I have heard that the 0W-40 works fine in cars that run 5W-30.

Lexusfreak

I agree with Lexmexico.....I'd stick with the 5W 30 Mobil 1 (I use the same in my car as well). You are correct however that your getting slightly better milage with the 5W 30 over the 10W 30 just because the oil is ever so slightly thicker & bevieve it or not, it makes a difference (not huge mind you as you didn't harm anything when you put the 10W in your car), but slightly noticable as you mentioned. The 0W maybe even a bit thinner than the 5W but would be "overkill" unless your living in the Antartic or something as thats for really "extreme" cold temps. How did you find the 5w 40 Lex? Was there a noticable difference in oil consumption?

Lexmexico

Actually have experimented again with the 5W-30, changing from a 15W-50. I still notice a loss in torque and a higher consumption than with the 15W-50. However, right now in Mexico City it is the cold part of the year, 50-65 deg. F (no joke). Will likely let it keep going on the 5W-30 for a short while, but will monitor the consumption. 5W-30 works like a charm on the road up to Texas and back in the States.

I knew a 5W-40 exists, but I have never seen it in Mexico. I heard people back in the States had trouble finding it. I know from my Australian friends there is a Mobil 1 5W-50. This would be ideal. The 50 weight seems to be really important here as you need torque with these hills. I know of specific cars that will not be able to get up certain grades of hills without a heavier oil.

Lexusfreak

I know Quaker State & Castrol both make a synthetic 5W 50 grade as well. Are they available in Mexico Lex? How often to you go to the U.S.?

Lexmexico

I have seen Castrol and Quaker State synthetics, but not in that grade. Amsoil was also available here, but at $15 a liter, and the distributor is based out of Monterrey. I can get Mobil 1 for about $9.99 a liter for 5W-30 and a little less, about $6.50 for 15W-50.

I did have a friend in Queretaro, north of Mexico City and a little lower elevation, with an ES300 who did try using one of those higher grades of Castrol, but had bad MPG, something I surprisingly have not had with 15W-50, then again I have a rougher terrain here that my RX benefits from using a higher weight.

The local mechanics swear synthetic is better, but if you go to any dealer, they will tell you regular oil is just as well. LOL

I only get up to the states every six months. Some people here and on bobistheoilguy.com suggested making a blend of different grades. Not to sure about this.