The findings of the trial judge relate to the purpose "for which the premises have been used." The degree to which the "original nature and purpose of the undertaking remain unchanged" determines whether there has been a change in a preexisting use. Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 662. We note that Butler testified that in addition to the sale of gasoline and oil, he sold tires, batteries, and anti-freeze. He also did car lubrication and fixed flats.

As the defendants' brief does not challenge that assertion we shall proceed in this opinion on the basis that the defendants do not care to raise any point that the case has become moot as to that plaintiff. Contrast Selectmen of Sudbury v. Garden City Gravel Corp. 300 Mass. 41, 42, 44 (1938); Wilbur v. Newton, 302 Mass. 38, 39, 42 (1938); Lexington v. Menotomy Trust Co. 304 Mass. 283, 283-284 (1939); Saugus v. B. Perini Sons, Inc. 305 Mass. 403, 408 (1940); North Reading v. Drinkwater, 309 Mass. 200, 201 (1941); Burlington v. Dunn, 318 Mass. 216, 221, 223 (1945), cert. den. sub nom. Dunn v. Burlington, 326 U.S. 739 (1945); Billerica v. Quinn, 320 Mass. 687, 688 (1947); Seekonk v. John J. McHale Sons, Inc. 325 Mass. 271, 272-273 (1950); Wayland v. Lee, 325 Mass. 637, 638, 639-640, 643 (1950); Lexington v. Simeone, 334 Mass. 127, 127-128 (1956); Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 658, 661 (1964); Stow v. Marinelli, 352 Mass. 738, 739 (1967); Goodwin v. Selectmen of Hopkinton, 358 Mass. 164, 166-167 (1970); Kelleher v. Selectmen of Pembroke, 1 Mass. App. Ct. 174, 176-178, 182 (1973); Byrne v. Middleborough, 364 Mass. 331, 332 (1973). See Butler v. East Bridgewater, 330 Mass. 33, 39-40 (1953); Kelleher v. Selectmen of Pembroke, 1 Mass. App. Ct. 174, 184 (1973); Byrne v. Middleborough, 364 Mass. 331, 332 (1973).

A better characterization is that the challenger must prove by a preponderance of the evidence that the zoning regulation is arbitrary and unreasonable, or substantially unrelated to the public health, safety, morals, or general welfare. See Sturges v. Chilmark, supra at 256; Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 659-660 (1964); Simon v. Needham, 311 Mass. 560, 564 (1942). As residential lot size requirements increase, it becomes more difficult to justify the requirements.

'" (Citations omitted.) Id. at 23, quoting from Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 662 (1964), and Medford v. Marinucci Bros. Co., 344 Mass. 50, 60 (1962). The property owner bears the burden of proving the requisite similarity between the current use and the original nonconforming use.

Simon v. Needham, 311 Mass. 560 (1942). Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 661 (1964). Cf. Euclid v. Ambler Realty Co. 272 U.S. 365 (1926).

Hinves v. Commissioner of Pub. Works of Fall River, 342 Mass. 54, involved the attempted enlargement of a nonconforming grocery store business by the addition of a commercial catering service involving the cooking of food. In Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, where the nonconforming use included the sale of crushed stone produced entirely from a quarry on the premises, we held, at 662-663, "that the importation of stone to be processed and sold on the premises as stone would be a change in use, and the petitioner has no right thereto." In Brady v. Board of Appeals of Westport, 348 Mass. 515, we held that a nonconforming use consisting of four or five boats associated with the premises moored or tied to a twelve foot pier could not be changed to a new structure consisting of two piers, one extending out into the water a distance of eighty feet and the other a distance of ninety feet, a barge measuring twenty-eight by ninety feet in size permanently affixed to the shore, and commercial boat repair and service facilities.

See Euclid v. Ambler Realty Co. 272 U.S. 365. See also Caires v. Building Commr. of Hingham, 323 Mass. 589, 594; Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 661; Anderson v. Wilmington, 347 Mass. 302, 304. But see Dooley v. Town Plan Zoning Commn. of Fairfield, 151 Conn. 304, 310.

The fact that improved and more efficient or different instrumentalities are used in the operation of the use does not in itself preclude the use made from being a continuation of the prior nonconforming use providing such means are ordinarily and reasonably adapted to make the established use available to the owners and the original nature and purpose of the undertaking remain unchanged. Superintendent I of Bldgs. v. Villari supra; Massachusetts Broken Stone Co. v. Town of Weston, 346 Mass. 657, 195 N.E.2d 522 (1964); Connecticut Sand Stone Corp. v. Zoning Bd. of App., 150 Conn. 439, 190 A.2d 594 (1963); Horwitz v. Dearborn TP., 332 Mich. 623, 52 N.W.2d 235 (1952); 58 Am. Jur. Zoning s. 165 (1948). See Bois v. Manchester, 105 N.H. 300, 199 A.2d 95 (1964).

The burden is on the petitioners to show the contrary. Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 660. Anderson v. Wilmington, 347 Mass. 302, 303. This is a heavy burden. Pierce v. Wellesley, 336 Mass. 517, 521. It also must be presumed that the voters of the town were familiar with the physical characteristics of the locality and the general nature of the neighborhood.

Recent cases have emphasized three tests for determining whether current use of property fits within the exemption granted to nonconforming uses. (1) Whether the use reflects the "nature and purpose" of the use prevailing when the zoning by-law took effect. Massachusetts Broken Stone Co. v. Weston, 346 Mass. 657, 662. Superintendent Inspector of Bldgs. of Cambridge v. Villari, 350 Mass. 176, 177-178. (2) Whether there is a difference in the quality or character, as well as the degree, of use. Brady v. Board of Appeals of Westport, 348 Mass. 515, 523. Building Inspector of Malden v. Werlin Realty, Inc. 349 Mass. 623, 624-625.