Jump to content

Recommended Posts

I searched but could not find an answer.  Is 85-octane regular OK to use on my RV?  I just got into Utah and Colorado and noticed that the octane ratings are: 85-regular, 87-midgrade, 91-premium as opposed to 87-regular, 89-midgrade, 91-premium that I have seen everywhere else.  I'm afraid of damaging my engine due to knocking.

I also cannot understand why 85-octane would be available on these states where mountain passes, high winds, etc... are a norm, I would think that the opposite would be true, that they would offer higher-octane rather than lower-octane to cope with these conditions, or am I just crazy thinking it doesn't make sense?

Related (but maybe unrelated), I've been keeping a log of my mileage (1990 Dolphin 3.0V6 Automatic) and with mostly highway driving and some in-National-Park-and-small-town driving I've done a best of 17.3MPG and worst of 15.5MPG, and this includes going over the Rockies into Denver (40MPH in 2nd gear on the steepest parts but then coasting most of the way down).  But, on flat level ground I stay around 60MPH.  Would using 85-octane lower my MPG also, as well as cause knocking?  Anyone?

IMG_1995.jpeg

IMG_1948.jpeg

IMG_2001.jpeg

Link to comment
Share on other sites

In other ICE motors that call for 87 or better that I have driven in high altitudes they were fine. Even when towing. I think the altitude allows one to use less octane. 

Link to comment
Share on other sites

The higher the octane the slower it burns so having a lower octane, quicker to ignite gas might help at high altitudes. Higher octanes do not offer any more power or fuel mileage. All they do is stop your engine from pinging. 

Linda S

Link to comment
Share on other sites

Choice between 85 and 87 go with the 87. Any thing above 87 is a waste of money unless you are driving a Porsche. Most gas now has ethanol, in itself that is not a bad thing ready for this anti ethanol guys? Its octane rating is right around 120! 

Link to comment
Share on other sites

  • 1 month later...

I've lived in the Denver area for 35 years, that octane difference has been true that entire time.  The physics of thinner air at higher altitude means less octane is needed here.  If you use "regular" (87) at lower altitudes, use "regular" (85) throughout most of Colorado.  As Linda noted above, try bumping to mid-range if you're experiencing pre-ignition (aka pinging). 

SOMETIMES (and it doesn't hold true in my '86 New Horizon) bumping to mid-grade will improve mileage enough to make it worth the higher cost - that'd be in a vehicle which isn't pinging, but still not quite getting the octane it needs for somewhat higher engine cylinder compression.  That's a trial-and-error experiment if your vehicle seems to not get the mileage it should.

BTW if you are at in-between altitudes, you can advance your ignition timing a few degrees & take out the knocking "by ear".  I used to do that in the good old Datsun Roadster sport car here in Denver, time it completely by ear.  Datsun for you young folks (under what, 50?) is what we call Nissan today - google Datsun Roadster or Datsun Fairlady for pictures.  

Edited by tstockma
Link to comment
Share on other sites

1 minute ago, Maineah said:

13.5 to 14.2 that's the best I ever did with a 22RE.

That's my MPG range pretty much and I've got my 22re dialed IN and running smoooooth.   Something worth noting is that I'm not confident that everyone's speedometers are accurate.  In my case somebody changed something along the way in my rig and it was about 6 mph high on the dash.  This makes the MPG much more optimistic without a correction. Then I changed the speedometer gear but didn't guess right.  now it's 3 mph high.  I've just received the next tooth down gear and I'm hoping to be closer to an accurate MPH reading on the dash.  I don't even keep track of MPH anymore because it's not like I can change it.  It is what it is and I fill it up when it's empty.

Has everyone claiming kind of high MPH actually calibrated their speed readings?  Easy enough with a free app on your GPS enabled smartphone...

Link to comment
Share on other sites

I drove a certain amount of mileage in between two towns and filled up the tank at the first town and then filled up the tank at the second town, and I got at least twenty one point five miles to the gallon. Unless the road Milestones are off, that's the mileage I got it from my 1982 Toyota sunrader

Link to comment
Share on other sites

The way I measure my mileage (and also save on gas) is by using the GasBuddy app on my phone.  I use it religiously, and I log every fill-up on there, it keeps track of your MPG, and it gets more accurate the more fill-ups you log.

But there are some things to keep in mind:

- It is (in my experience) 100% accurate as far as the prices, BUT, some gas stations (ARCO's, notably) give you the lowest CASH price, but then when you use a credit or debit, the price is higher, and often higher than other stations CREDIT prices... doh!

- While in AZ and CA, I had it set for "Regular", but as soon as I crossed into UT, and I went to the first gas station, I noticed that regular had become 85-octane, and now regular was "mid-grade" 87-octane, and in some parts (Idaho, I think), they had TWO midgrades, one at 87 and one at 89, so a total of 4 grades... doh!  Keep this in mind if you set it to search "midgrade" gas prices.

- Without fail, the best prices were always at Costco, so..  yeah.

- You get points by contributing to the app, either entering prices that you see or confirming the prices.  What are points good for?  Who knows?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...