Have a RX-350 [117K miles]....questions:
1] Started using Shell premium gas a month or so ago [after using regular since i bought car used with 36K]....maybe a 2 mile per gallon mileage improvement..but cost of premium is $3.34 /gal vs. $2.44 /gal for regular....hard to swallow...will i be increasing the life of the engine if i continue to use premium?

2] How could i prevent contamination of battery cables...had to get one cable replaced as it was turning green[ positive terminal].

Thanks for helping.

 

There are wars over premium vs. lower grade. Personally, yes, I've noticed better performance with premium but many say otherwise. On my last car (2001 Highlander) I wrecked the catalytic converter through my consistent hunt of cheap gas, very heavy bill. Costco is how I get my gas, the savings are significant.

Also battery contamination can be prevented with a terminal spray you can buy at many auto parts stores. It's usually red but can come in different colors, I know Toyota dealers use red.

 

Where you get your fuel is more important than the grade of fuel. That said, if you push your engine hard stick to premium. If you are an easy driver then you should be fine with regular. On an engine designed for premium fuel the ecm will use default timing until the knock sensor detects pre-ignition. At that point it will, engine cycle by engine cycle retard timing until it gets no more knock indication. In normal driving this is no big deal - if you push your engine hard there is a remote possibility of damaging the engine before the system can eliminate pre-ignition. Note that it would likely be a long term issue unless you are very unlucky.

I use premium in mine although I rarely push it very hard. You might consider trying a mid-grade and see how that works for you. Again, get your gas from a reputable station and avoid the cut-rate stations as that will do more for the long term health of your vehicle.

 

Lexuswiz: Do you use Cotsco premium...think it is 91 or their regular...thanks.

 

91 on my RX330, 87 on my Camry (whenever I can take it there). Depending on where you are it can range from 91-93, but still good stuff, I like it.

 

I'm sure this has been said before but shouldn't you just follow the recommendation in your owner's manual ? You paid higher money for your Lex, why not take care of it ? Also, not mentioned yet but probably as important is to make sure you use "Top Tier" gasoline, which has a higher amount of detergents to keep valves, etc clean. Also gas sold which has been certified top tier cannot contain metallic additives which damage emission systems (i.e. Catalytic Converters).

Costco Gas is Top Tier Gas - same for Shell. I use High Test at Costco whenever I can, and use Shell if I'm not close to a Costco.

I also put Costco/Shell in by old but trusty 95 Tacoma v6 but luckily I don't need high octane in it.

Just google Top Tier Gas to see which brands sell it vs. the brands that are junk....

 

Every now and then when washing ours, I mix a little baking soda and water and pour it on the green crud. Rinse thoroughly so nothing is trapped in the battery pan.

 

Best prevention for corrosion, take a dab of very light grease and apply on the positive and negative poles. This acts as barrier for the battery fluid encroaching the terminals and therefore will minimize-avoid corrosion-reaction.

 

Does the 3.5l "require" premium? I know on the 3.3l it is not at all required but more "suggested" in the owners manual to use premium for maximum performance. If I remember correctly you 350 guys might not have the option per Lexus.

 

The 3.5L recommends premium, but will take an 89 Octane. If you were a Costco member, the price of premium is equal to the price of mid-grade 89 of brand name gas stations.

 

The positive battery terminal was heavily covered with oxidation when I first purchased the RX330, Battery Terminal Cleaner worked very well, 3 months later, the terminal appears to be still protected & clean.
Try mid grade gasoline, if the RX doesn't like it, it will tell you & switch back to Premium if needed be.

 

I recently did some research on gasoline. Apparently it is just as important to use Top Tier gasoline as it is to use the correct grade. I was using Eagle gas until I found out it's not Top Tier. The Top Tier gasolines use the correct additives to prevent corrosion and this is as important, if not more important than using a higher grade of gas. So I've switched to either Shell or Citgo. Also, I don't use premium. I use the middle grade, usually 89 octane, with no harmful results. When I use premium, there is no difference in MPG and we never have any pinging. So until I find some reason to change, I'll continue to use the middle grade gas, but I will switch to top tier gas only.
As for the battery cable. So far we're good on our 2009 RX, but our 2005 Highlander that uses the same cable, had to have a replacement around three years ago. It's a poor design. We tried using the grease coating mentioned above and tried the protecting paint, nothing worked. I'm just resigned that around every 10 years, the positive cable needs to be replaced.